^^Bf ^^pi ' a ! a i LOJ : a ' fc- 1 i i i a a JT -O nj 0= !H MANUAL OF ENTOMOLOGY, - MANUAL OF ENTOMOLOGY, TRANSLATED FROM THE GERMAN OF DR. HERMANN BURMEISTER, BY W. E. SHUCKARD, M.E.S. WITH ADDITIONS BY THE AUTHOR, AND ORIGINAL NOTES AND PLATES BY THE TRANSLATOR. MORMOLYCE PHTLLODES. LONDON : EDWARD CHURTON, PUBLIC LIBRARY, 26, HOLLES STREET. 1836. LONDON : tND EVANS, PRINTERS, IVIltTFFIUARS. PREFACE. UPON completing the Translation of this < Manual,' it is incumbent upon me to thank the press generally for the very favourable reception it has obtained throughout its progress. It was undertaken with the view to contribute to the advancement of the study of Entomology, by giving a wider circulation to its elementary principles ; and it is hoped that its interesting details will tend to diffuse a taste for its more general cultivation. Amidst a multitude of original experiments and observations, in addition to its numerous other scientific claims, this work will be found to comprise, in its anatomical and physiological depart- ments, a generalisation of the host of facts elicited by the laborious investigations of Straus Durckheim, Miiller, Suckow, Leon Dufour, Nitzsch, &c. &c., up to a very late period. It is confidently believed, that a book combining the researches of such eminent men must necessarily become extremely useful, not only to the entomological but also to the physiological student, and to the scientific man in general. i The advantages to be derived from the study of natural history are manifest. One of its most conspicuous merits, and that upon which the immortal Cuvier particularly dwelt, is its tendency to methodise the mind, by impressing it with a habit of VI PREFACE. order and precision ; thus, having all the effect, but under a more alluring mask, of the abstract mathematics, and the logic of the schools. This character attaches more peculiarly to that portion of natural history upon which this work exclusively bears namely, the STUDY OF INSECTS. Their great multitude and diversity, their brilliancy of colour, eccentricity and extreme elegance of form, their metamorphoses, complexity of structure, and peculiarities of habits, always adapted to the purposes they have to accomplish in the economy of nature, altogether unite to give an intense interest to this delightful pursuit. Having thus summarily shown the value of the work, and the utility and pleasure to be derived from the study of the science, it only remains for me to add my best thanks to DR. BURMEISTER for the promptitude with which he spontaneously supplied me, upon hearing of my undertaking, with the new MS. of several portions wherein his opinions had become modified or changed. THE TRANSLATOR. TABLE OF CONTENTS. PAGF. Introduction Definition and Compass of Entomology, 14 . 1 FIRST DIVISION. GENERAL ENTOMOLOGY. FIRST SECTION. ORISMOLOGY. Its Definition and Compass, 57 . . . . b FIRST CHAPTER. General Principles, is 13 . . 7 SECOND CHAPTER, General Orisraology, $14 . ,11 I. Form, 1521 . . . 11 II. Quality, 2224 < . . .16 III. Clothing, 25, 26 .19 IV. Colour, 27 38 . 20 V. Measure, 39 42 . . . 2H VI. Affixion, Direction, 43 45 , . 2 Vlll TABLK OF CONTENTS. THIRP CHAPTER. PACK Partial Orisiuology, 46, 47 . 30 I. The Egg, 48 50 . . 31 II. The Larva, $$51 58 . . 33 III. The Pupa, 59 64 . 43 IV. The Imago, 65 . 48 1. The Head, $66 72 . . 49 The Mouth, 6870 . .51 The Eyes, 71 .62 The Antenna;, 72 . 63 2. The Thorax.. 7378 . 71 Organs of Motion on the Thorax. A. The Wings, 79, 80 .91 B. The Legs, 8183 . 100 3. The Abdomen, 84, 85 . . 108 SECOND SECTION. ANATOMY. Idea and Subdivision of it, 8690 .114 FIRST SUBSECTION. VEGETATIVE ORGANS. Their general Character, $$91 94 .1 17 FIRST CHAPTER. THE ORGANS OF NUTRITION.' 1. The Intestinal Canal and its Appendages, 95 114 . 1 19 II. The Fatty Substance, 115 .151 I IF. The Blood-vessels, 116121 . 153 IV. Tlip Organs of Respiration, 122 130 TABLE OF CONTENTS 1\ SECOND CHAPTER. THE ORGANS OP GENERATION. PAGE Their general Character, 131 134 . . .181 I. Female Organs of Generation, 135 145 . . 184 II. Male ditto, 146152 . . 200 III. Development of the Sexual Organs during the Metamorphosis, 153 . . ... 220 IV. Conformity of the Female and Male Sexual Organs, 154 . 222 SECOND SUBSECTION. THE ANIMAL ORGANS. Their general Character, 155157 . . . 224 THIRD CHAPTER. THE ORGANS OF MOTION. I. Of the Horny Skeleton, 159168 . . 226 II. The Muscular System, 169181 . . 247 FOURTH CHAPTER. THE ORGANS OP SENSATION. Their general Division and Character, 182 . . . 269 I. The Brain, 183 185 . .272 II. The Ventral Cord, 186 188 . . .277 III. The Sympathic System, 189 191 . . 2*6 IV. The Organs of the Senses, 192198 . 289 THIRD SECTION. PHYSIOLOGY. Its idea and subdivision, 199200 . . . 302 FIRST SUBSECTION. SOMATIC PHYSIOLOGY. Its idea, 201 . 304 TABLE OF CONTENTS FIRST CHAPTER. PAGE Of Generation, 202213 . . . 306 SECOND CHAPTER. Of Nutrition. Its general character and kinds, 2J4 216 . . 344 I. Digestion, 217225 . . . 347 II. Respiration, 226236 . . 384 III. Circulation of the blood, 237 243 . . 403 THIRD CHAPTER. The Metamorphoses, 244260 . 414 FOURTH CHAPTER. The Muscular Motion, 261267 . . .445 FIFTH CHAPTER. The Sounds emitted by Insects, 268271 . 466 SIXTH CHAPTER. Of Sensation and the Senses, 272 278 . . 474 SEVENTH CHAPTER. The Luminousness of Insects, 279282 . . . 490 SECOND SUBSECTION. PSYCHOLOGICAL PHYSIOLOGY. The Nature and Object of Instinct, 283286 . . 498 EIGHTH CHAPTER. THEIR SELF-PRESERVATION. I. Means of Defence, 288 . . 504 II. Instinct of Nutrition, 290 . 511 TABLE OF CONTENTS. XI NINTH CHAPTER. THEIR MEANS FOR THE CONSERVATION OF THE SPECIES. PAGE Sexual Instinct, 291 ..... 513 I. The Copulative impulse, 292 . . . . 513 II. Affection for their young, 293 299 . . 515 THIRD SUBSECTION. RELATIONS OF INSECTS TO THE EXTERNAL WORLD. Compass of this relation, 300 . . . 537 TENTH CHAPTER. IN RELATION TO OTHER ORGANIC BEINGS. To Plants, 301306 . 538 To Insects, 307 . 552 To Birds, 308 . . . 554 To Mammalia, 309 . . 556 To Man, 310 . . . 558 ELEVENTH CHAPTER. Relation to the Elements and Seasons, 311 313 . 565 TWELFTH CH.4PTER. Relation to the Antediluvian World, 314317 574 FOURTH SECTION. TAXONOMY. FIRST CHAPTER. General ideas Nature of Artificial and Natural Divisions, 318321 582 I. Idea of Species, 322324 . . 588 II. Idea of a Genus, 325331 . 590 III. Idea of the Higher Groups, 332336 . 594 Xll TABLE OF CONTENTS. SECOND CHAPTER. HISTORY OP THE PRINCIPAL SYSTEMS. PACK Earliest essays, Aristotle, 337 . 597 More recent ones, 338343 . 598 Zootomical systems, 344349 . 608 Physiological systems, 350 352 . 617 THIRD CHAPTER. Nomenclature, 353363 624 INTRODUCTION. DEFINITION AND COMPASS OF ENTOMOLOGY. 1. NATURAL HISTORY has for its object the inquiry into the being of natural bodies and their thorough investigation in reference to their various qualities, and the relative functions of their component parts. Understood in this extent, it presents us with a distinct unique entirety, which treats the natural body as complete, but gradually perfected ; and at the same time seeks to discover the means whereby it attained its completion and perfection. Natural History, therefore, is no mere description of form, no description of nature, as it has been, latterly, very 'incorrectly considered, but a true, and pragmatical history, developed from its own fundamental principles. ENTOMOLOGY is that branch of this extensive science, which treats of the Natural History of Insects. Insects are animals with articulated bodies divided into three chief portions, the head, thorax, and abdomen ; they have three pairs of legs, and generally two pairs of wings, and, to acquire this structure, pass through several transformations and changes, called their metamorphoses. The object of Entomology, consequently, is to investigate the nature of insects ; its design is to show how the insect is organised and formed, and why it was obliged to adopt this particular conformation and internal structure; and when this is accomplished, it proceeds to the generalisa- tion and development of the various vital phenomena observable in the class. Its view is, however, not limited here to show the mere gene- ral form of the body of the insect, but it also displays how this general B 2 INTRODUCTION. form varies in the several orders of insects., and how far this transfor- mation and change may extend without destruction to its identification. This comprises, therefore, a summary of the essential purpose of the science. The chief incentive to our study, and investigation, of natural bodies in general, is the instinctive impulse of the human mind towards progressive information, and the extension of the circle of its knowledge; but, in this pursuit, a multiplicity of useful discoveries are made, which are applicable to daily life, and which distinctly show the evident advantages of the science, although their elicitation can never be consi- dered the primary object of scientific research. The study of insects will likewise be found rich in similar results, which I shall state in its appropriate place. 2. Thus, the Natural History of Insects falls into two great divisions viz. the introductory, or general portion, and the particular, or systematic Natural History of them. The former, or general division, acquaints us with insects with respect to their exterior construction, and with regard to their interior organ- isation ; it also instructs us of the various phenomena displayed by this class of animals ; and lastly, developes the principle upon which insects must be arranged, and naturally subdivided. The following divisions are thence deduced: 1. The ORISMOLOGY, generally called the Terminology *, which contains the various technical terms used in explaining the perceptible differences in the body of an insect, and at the same time acquaints us with its exterior visible parts in the several periods of its existence, until its full and perfect development. 2. The ANATOMY, or, as it has been called, in reference to the dissection of insects, ENTOMOTOMY, which acquaints us with their in- ternal construction,' and with the form as well as texture of their organs. 3. In their PHYSIOLOGY we learn the functions of these organs. Besides which, it generalises the multifariously varied phenomena dis- played by these animals, and re-examines, under a general view, those to which we are accustomed to apply the name of instinct. * Kirby has introduced the term ORISMOLOGY in lieu of the hybrid compound TBIIMINOLOGY, but which being derived from 'opiff^os (terminus, dejiitltio) should be written Horismology. But as it is not unusual to reject the spiritus asper, we have retained his orthography. INTRODUCTION. 3 4. This is succeeded by their TAXONOMY, or principles of arrange- ment, which, after giving its general rudiments, proceeds with a critical survey of the most remarkable Entomological systems. 3. The second or particular division of Entomology, contains merely the description of the insect world, from their highest to their lowest sub-divisions, in the mode most consonant with system and their scien- tific definition. It is this portion which is generally called systematic Entomology, or plainly Entomology, and which is both the most com- prehensive, and most varied portion of the whole science. 4. These, therefore, are the several divisions of which the complete Natural History of Insects consists ; they are all closely connected together, and produce, only by their strict union, that harmonious en- tirety of which the science boasts; whereas, the several parts, considered separately- form but dislocated fragments, each of which, without the elucidation of the rest, must frequently remain incomprehensible. The subdivision of insects into orders, groups, and families, does not properly belong here, but will find its true situation much lower, where we pur- pose passing to the particular description of the individuals of this class ; but as, in the course of the following treatise, we shall so frequently have occasion to refer to the several orders, it will perhaps be consi- dered not inapposite, particularly as it may assist the judgment of Tyros, if we here lay down the distribution into groups. It may remain here merely intercalated by anticipation. The commencement of this introduction has already denned what an insect is ; all animals comprised in it may be thus classed into A. Those with an imperfect metamorphosis, i. e. larva, pupa, and perfect insect, strongly resembling each other, the pupa possessing loco- motion and eating. a, having a suctorial mouth. 1. ORDER. HEMIPTERA. (Cimices, Bitgs,$c.) b. having a masticatory mouth. a. Four unequal wings, the superior ones pergameneous, the inferior generally larger, and membranous ; the latter are folded in repose. B2 4 INTRODUCTION. 2. ORDER. ORTHOPTERA. (Locusts, Grasshoppers, ffc.) b. Four sometimes equal, sometimes unequal membraneous wings with reticulated nervures, but never folded. 3. ORDER. DICTYOPTERA. (Cockroaches.} B. Those with a perfect metamorphosis. The larva is a long maggot, caterpillar, or wornil. The pupa generally quiescent, and does not eat. a. Some have a suctorial mouth. a. Insects with two naked transparent wings. 4. ORDER. DIPTERA. (Ffe.) b. Insects with four large wings, covered wholly, or partially, with broad scales. 5. ORDER. LEPIDOPTERA (Butterflies, Moths.) b. The others have a masticatory mouth, or at least visible man- dibles and palpi. a. Four equal wings, with reticulated nervures. 6. ORDER NEUROPTERA. (Dragon Flies, $c.) b. Four unequal wings, with the nervures variously branching. 7. ORDER. HYMENOPTERA. (Sees, Wasps, Ichneumons, $c.) c. Four unequal wings, the superior ones consisting of a corneous case. 8. ORDER. COLEOP-TERA. (Beetles.) Note. Throughout almost all the orders there are apterous families, genera, and species, which are very easily referred to their orders from their metamorphosis, and the structure of their mouths, but they never form correctly a distinct one, as Latreille insists, and which he calls APTEKA. FIRST DIVISION. GENERAL ENTOMOLOGY. FIRST SECTION. ORISMOLOGY. ITS DEFINITION AND COMPASS. 5. IN a science, which, like Natural History, has to distinguish such multifarious, and, frequently, such closely approximate forms, it is of great importance that the differences perceptible to the eye should be explained by a suitable selection of precise terms, and in a clear, concise, and readily comprehensible language. Since the recognition of this principle, a kind of conventional agreement has been aimed at, whereby the Latin language still retains, at least in the descrip- tive natural history of the animal and vegetable kingdoms, that degree of importance which it acquired by its introduction as the universal language of the learned. The technical language of natural history thus therefore originated ; for, in the course of progressive investigation, new terms were required to characterise the newly dis- covered parts. 6. Following the example of early writers, whenever the Latin lan- guage is deficient in the characteristic expression, we apply to the Greek, and endeavour to derive from it an appropriate name, or form I GENERAL ENTOMOLOGY. one from it by composition. From the euphony of its words, and the fulness of its tone, it is peculiarly adapted to the construction of permanent names of general importance, and has therefore found a suitable application in the naming of newly discovered orders, families, and genera. In the construction of these names, however, we must be exceedingly careful not to wound the spirit of the language by barbarisms, grammatical inaccuracies, and hybrid compounds (e.g. Bitoma, Biphyllus, Taxicornes, &c.), of which, unfortunately, too many disagreeable examples could be cited. But it is decidedly wrong to retain these inaccuracies, although such words may have derived a certain authority from their age, from the mere accident of the inad- missible nature of their composition not being previously discovered. The love of truth and correctness demands that such blemishes should be expunged, wherever they are found, and they can never be subject toother considerations ; for esteem for their authors, which they may, in other respects, justly merit, must not prejudice us in their favour. 7. The technical language of Entomology is subdivided into three parts, which may be here concisely indicated. The FIRST chapter contains the important and indispensably neces- sary general rules and principles for properly naming newly discovered parts. The SECOND chapter treats of the general qualities of all, or many organs, which are comprehensible without a knowledge of their peculiar forms ; but, on the contrary, in the description of the latter, must be frequently referred to. The differences of colour, and of clothing, annex themselves hereto. GENERAL ORISMOLOGY. In the THIRD chapter I shall explain the various parts and organs of the body of an insect, as well as their peculiar differences. PARTIAL ORISMOLOGY. (Kirlys Exterior Anatomy.) OF.NEK.U, I'lUNCIPLKS. FIRST CHAPTER. GENERAL PRINCIPLES. ALTHOUGH we here, at once, declare ourselves opposed loan unne- cessary multiplication of orisaiological terms, yet we do not mean that the determinate distinction of particular parts should be rejected, whenever they are decidedly important. On the contrary, it is the very first requisite of a precise orismology to npply an exclusively proper term to each constantly distinct and peculiar part. It will certainly appear often difficult to restrain oneself within exact limits, particularly as there are but few other general principles to guide ns than a certain, judicious, and intuitive tact. We will, however, com- mence by endeavouring to lay down a few principles as rules to be observed. 9. I. Every decidedly different organ, or, where it appears necessary, every portion of an organ, should receive a name exclusively peculiar to itself. II. This naming, however, must not be arbitrarily exercised; but the organs of the superior animals must be consulted, and their analogical structure examined in the insect *. The greatest mistakes have, at all times, been made in opposition to this principle, and yet it is as absolutely necessary, and as strictly founded in the very nature of the thing, as any. It has doubtlessly occasionally proceeded from an ignorance of the anatomy of the higher animals ; perhaps, also, from the love of innovation of many writers, that the most singular interpretations have been made, names having been applied to parts, or merely portions of organs, which, strictly, could be applied only to very different organs. To call that part, the neck (collum), which bears the legs, is absolutely absurd. Even Fabricius's division of the body of an insect into caput, truncus, and abdomen, is wrong, as every one who knows anything of anatomy must admit that the truncus includes the abdomen. In the course of our observations we shall detect many similar inconsistencies, but we have generally considered it unnecessary to take further notice of them, confiding in the correct judgment of the reader. We have, indeed, endeavoured to retain, as far as was possible, what has been already done ; but we make it a rule to adopt nothing that is false, whatever may be its antiquity, ami notwithstanding its toleration l>\ the great masters of the science. 8 GENERAL PRINCIPLES. 10. III. Great caution must be exercised in the naming of different parts in the several orders, as, frequently, the same organ in the different groups takes a very different form. If particular names were applied to such modifications, it would tend to mislead, by giving the appearance of different parts to one and the same. Nor is the reverse of this admissible, for different organs must not bear the same name *. 11. IV. The names of parts should be derived, in prefereuce, from Latin, but it is advisable in those parts which have always been signified by Greek terms, to retain them, and introduce new Greek ones whenever new parts are discovered within the limits of the particular organs f . V. Peculiar organs, which, nevertheless, can only be considered as variations of a long known typical form, are best distinguished by an adjective expressive of the peculiarity. E. g. The legs are called pedes; when adapted to the seizing of prey they are suitably called pedes raptorii,not arms (brachia) according to Kirby. The idea of arms presumes a certain organisation which is never found in insects, although the raptorious legs of insects may possibly be analogous in their functions. But it is certainly incorrect to call the anterior legs of insects in general arms; we might just as rationally call the fore legs of quadrupeds arms. Swimming legs are thus called pedes natatorii, but not fins (pinnae). * Fabricius made a mistake of this kind, in applying to what he had called truncus, in the Coleoptera, the name of thorax, in the Hymenoptera and Diptera ; and, in calling by the latter term the anterior portion only of the same part, in the Coleoptera, Hemiptera, and Orthoptera. As in each of the orders of insects, the thorax consists of three parts, which have been distinguished as prothorax, mesothorax, and metathorax, it is evidently incorrect to call that collare, in the Hymenoptera, which is called prothorax in the Coleoptera, Hemiptera, and Orthoptera ; for the same orismology must be applied to every order. Reasoning upon the same principle, we cannot see why that portion of the head should be called hypostoma, in the Diptera, which, in the other orders, has long been indicated by the name of clypeiis. | It consequently appears preferable to us to call the first segment of the thorax the prothorax, rather than collare, exclusive of the greater precision and comprchensibility ot llu- first term. I. GENERAL PRINCIPLES. 9 VI. In many such cases, however, where the substantive is borrowed from the Greek, a new word is formed by the compounding of two, e. g. hemelytra, prothorax, &c. 12. VII. All fluctuating qualities of one and the same part are distin- guished by adjectives, and indeed by such as, according to grammatical use, are customarily applied to such variations. But the form of the adjectives, which express particular kinds of qualities, vary chiefly in their terminations. The following are important for our use : 1. The termination in atus and itus, shows merely the existence of something in general : for ex. antennatus, provided with antennae ; alatus, winged ; sulcatus, with longitudinal furrows ; auritus, furnished with ears (two little appendages). 2. The terminations in aceus and icius express a resemblance to a material ; those in em indicate the material itself: for ex. membranaceus, resembling skin; membraneus, skin itself ; coriaceus, leathery ; lateri- cius, resembling bricks (in colour). 3. The termination osus expresses fulness, or the abundant presence of a quality : for ex. pilosus, covered with much hair ; setosus, covered with stiff bristles ; squamosus, covered with scales. 4. The termination ius expresses the uses or aptness of an organ : for ex. raptorius, adapted to seize prey ; fossorius, fitted for digging ; natatofius, suited to swim, &c. 5. The deficiency of a usually present quality is indicated by placing in front the a privative in the Greek, and the preposition e, ex, or in, in Latin words : for ex. apterus, without wings ; escutellatus, without a scutellum ; iner.mis, unarmed. 6. To express quantity or particular distinctness, the superlative degree of comparison is used, or the words valde, maxime, distincte, are prefixed : for ex. squamosissimus, densely covered with scales ; rugo- sissimus, very uneven ; distincte-punctalus , very clearly covered with punctures. 7. The indistinctness of a quality is expressed by prefixing the word obscure, or by uniting the preposition sub to the adjective. But diminutives are not unfrequently used : for ex. obscure-ceneus , of an indistinct bronze colour ; subpunctalus, slightly punctured ; snbstriatus, slightly striated; hirsutiuscuhis, somewhat hairy. 10 GENERAL PRINCIPLES. 8. To express a quality which is directly the reverse of the usual signification of the term, the particle ob is added, and we say, for ex. obconicus, of the shape of a reversed cone ; viz., when a part, instead of running from the base upwards to a point, runs from the apex down- wards to the point ; obovafus is used in the same way to express its being of a reversed egg-shape. 9. Qualities which consist of the conjunction of two generally separated peculiarities are also expressed by the union of both the adjectives. In composing these words we must be particularly cautious in the succession of the united terms, as it is by no means indifferent. The word expressive of the dominant quality stands last, and that made to precede it is merely its modification : for ex. puuctatus indicates being covered with punctures ; striding, having linear longitudinal impressions. By the various compounding of these two words, very different ideas are formed, according to their precedence. Striato- punctatus indicates a surface which is merely punctured, but the punctures whereof are placed in rows ; punctalo-strialus, on the contrary, is a surface which has distinctly impressed lines with punc- tures within. 13. VIII. Parts which discover a certain resemblance of form with objects, Avhich, by their application, or uses in common life, are suffi- ciently known, are suitably named from what they accord with. Many adjectives thence occur in Orismology which require no further expla- nation. This is not so usual in the terms expressive of colour, and particularly where it is desirable to explain the multifarious transitions of one into the other, \ve meet with difficulties in the selection of the exactly appropriate word, so that peculiar orismological terms are requisite for their correct definition. GENERAL OlllSMOLOGY. 1 1 SECOND CHAPTER. GENERAL OlllSMOLOGY. 14. THIS portion of Orismology has not the advantage of a consecutive arrangement derived from the nature of the objects contemplated, for it can be regarded only as consisting of a mass of equivalent ideas, with their applicable and variable attributes. But the best arrangement appears to be that of passing from the most general to the more partial terms ; we have thought, therefore, but without wishing to prescribe it as necessary, that the most agreeable mode would be to proceed from the general form of parts to the differences of colour, clothing, size, direction, &c. I. THE FORM. 15. The differences of form may be considered, doubtlessly, as the most multifarious throughout the whole class of insects ; it will not there- fore surprise that this portion of Orismology is very rich in terms. But even this very great diversity leads us to conclude that certain forms are peculiar to a few organs only. All distinctions, therefore, which have merely this restricted application, are necessarily excluded from our immediate general consideration. 16. If we take any part and contemplate it in its natural connexion with the rest of the body, the following portions may be clearly distinguished in it : BASE (basis), that portion whereby it is affixed to the body. APEX (apex), that which is opposed to the base. CONTOUR (peripheria), a portion whereof is the MARGIN (niargo). According to its situation, this is distinguished into anterior margin, that which is directed towards the head of the insect ; posterior margin, that directed towards its tail ; and lateral margins, those intervening between the anterior and posterior. 12 GENERAL ORISMOLOGY. SUPERIOR SURFACE (superficies externa), the INFERIOR SURFACE (sup. internd), the centre of the superior surface or DISC (discus), the border surrounding the disc or LIMB (limbus). ANGLE (angulus), is that portion where two parts or the margins of one meet ; SINUS (sinus), is a curved break in an otherwise straight margin; KEEL (carina), is a sharp, longitudinal, gradually rising elevation upon the inferior surface. 17- Besides these general definitions, which may be applied to all or very many organs, the differences of form may be contemplated under the following heads : 1. Differences of Surface. 2. Differences of Solids. 3. Differences of Margin. 4. Differences of Apex. 5. Differences of Base. 18. Figure of the Superficies. CIRCULAR (rotundum, circulare), is a round surface with its diameter equal on all sides. ROUNDED (rotundate), when the margins pass gradually into each other, and not meeting in sharp angles. OVAL (ovale), a rounded surface, its two right angular diameters being of an unequal length, so that its longest transverse diameter does not pass through the middle of its longitudinal diameter, but lies nearer to one end. ELLIPTICAL (ellipticum), allied to the preceding, but differing, inas- much as that its greatest transverse diameter passes through the centre of the longitudinal. LANCEOLATE (lanceolatum), when the base is not so broad as the centre, and the lateral margins slightly, but equally, swollen, gradually tapering towards the apex, where it terminates in a point, and the longitudinal diameter more than three times the length of the transverse. LINEAR (lineare), a figure having the lateral margins very close together, and parallel throughout. HALF-.MOON SHAPED (lunare), a figure formed by the portion of a circle cut off by the segment of a larger circle. GENERAL ORISMOLOGY. 13 HEART-SHAPED (cordalum), a triangular figure, having its base emarginate, lateral angles rounded, and lateral margins slightly swollen. KIDNEY-SHAPED (reniforme), is a half-moon shaped figure, with its angles rounded, and its concave margin emarginate. TRIANGULAR (triangulare), when the margins meet in three angles. SQUARE (quadratum), when the four straight parallel margins are of equal length. QUADRANGULAR (quadrangulare) , when two of the nuij^ms arc of unequal length. OBLONG (oblongum, parallelogramum), a square with two of the parallel margins equal, but longer than the other two equal parallel ones. ANGULAR (angulatum), when the angular margins do not exclusively elbow outwards, but also inwards. FALCATE (falcatum), a figure formed by two curves bending the same way, and meeting in a point at the apex, the base terminating in a straight margin, resembling a sickle. SPATULATE (spattdatuin), a figure commencing with a narrow base, gradually widening by the lateral margins sloping out, and terminated at the extremity by a sudden straight line, (the antennae of many Tachina and other Diptera). LOZENGED (rhomboidaE), a quadrangular figure, with two opposite angles acute and two obtuse. 19. forms of Bodies. SPHERICAL (globosum, sphcericuin), a round body, having all its diameters equal. HEMISPHERICAL (semiglobosum, hemispheericujri), a round body, terminated on one side by a flat circular surface. LENTICULAR (lenticular e), a round body, with its opposite sides convex, meeting in a sharp edge. CONICAL (conicum), a round body, the base of which is a flat circle and the apex a point. SUBULATE (subulatum) , a long thin cone softly bent throughout its whole course. COLUMNAR (teres*), a form the circumference of which is always circular, but its thickness indeterminate. CYLINDRICAL (cylindricum), a body with its circumference round, of indeterminate length, but equally thick throughout. 14 GENERA f, OKISMOLOGY. ATTENUATE (attenuatum), a cylinder having its transverse diameter much narrower in one part. EQUAL (equate), a substance of variable longitude, but the transverse diameters of which are equal. INCRASSATE (incrassatuni), much swollen at one portion of its length. CLUB-SHAPED (clavatum), a form which gradually increases in thickness towards its apex, where it is obtuse. PEAR-SHAPED (pyrijbrme), a similar shape, but with this difference, that its longitudinal section is spatulate. FUNNEL-SHAPED (infundibulifbrme), resembling the last in exterior form, but scooped out at its apical margin. FORNICATE (fornicatum), concave within and convex without. KNOTTED (nodosum), a longitudinal body swollen at one or more parts. ANGULAR bodies are distinguished by the number of their sides, viz. three sided (triquelrum), four sided (telragomim), &c. PRISMATIC (prismalicum), an angular body of indeterminate length but equal thickness. PYRAMIDAL (pyramidale), a triangular body, the angles of which all meet in one point. WEDGE-SHAPED (cuneaium), a body whose horizontal longitudinal section is quadrate, and perpendicular transverse section triangular. 20. Differences of Margin. ENTIRE (integer), a plain, flat, straight, or bowed margin, without angle or incision. ARCHED (arcuatu,?) a margin in the form of a bow. SINUATE (sinuatus), a margin with a rounded incision. WAVED (undulatus), a margin with a series of successive arched incisions. SERRATE (serratus), with jagged incisions, like the teeth of a saw. CRENATE (crenalus), a margin with indentations, the exterior whereof is rounded. DENTATE (dentatus), when the incisions are larger, causing the margin to stand forth free and direct like teeth. CILIATE (cilialus), when it is occupied with short stiff hairs. LOBATE (lob at us), when the margin is divided by deep undulating and successive incisions. EROSE (erosus), when from the irregularity of its incisions it appears gnawed (the margins of the wings of many butterflies). GENERAL ORISMOLOGY. 15 TKNTACULATE (tenlaculatus), when soft tensile excrescences are found upon the margin (Caniharis, Malachius). CALLOUS (callosus), a margin which resembles a thick swollen lump. MAKGINATE (marginal us), is when the sharp edge is margined, and surrounds the surface with a narrow border. DEFLEXED (defle,rus~), when this sharp edge is bent downwards. DILATED (dilatatus, or amplificatus] , when the sharp marginal edge extends beyond its usual limits. INCRASSATE (incrassaius), a margin whose edge is not sharp, but rounded, and somewhat swollen. 21. Differences of Base and Apex. The few distinct differences of the base refer merely to its greater or smaller width, and robustness. ANGUSTATE (angustalum), or COARCTATE (coar datum), is where a part begins with a narrow base, and then dilates and thickens. DILATED (dilatatum), a distended part, the transverse diameter of which is much longer at one particular part, and this peculiarity is generally found near the base. The differences of apex are much more varied ; we may enumerate the following as particularly important. TRUNCATED (truncalum), when a part is limited at the end by a straight line or surface. ROUNDED (rotundatum}, when the end takes the form of a segment of a circle. PREMORSE (pr&morsHm*), when the end appears bitten off or splintery. EMARGINATE (emarginatum), when the end has an obtuse incision. RETUSE (retustim), when the terminal margin has an obtuse im- pression. OBTUSE (obtusiim}, indicates a rounded termination. ACUTE (acutum), when it becomes regularly narrower and terminates in a point. ACUMINATE (acuminatum] , when this decrease is very gradual, becoming thereby much longer. MUCRONATE (mucronatum) , when from an obtuse end a fine point suddenly proceeds. CUSPIDATE (cuspidatuni), when this pointed process is very much extended, becoming almost setiform. r l(j GENERAL ORISMOLOGY. II. QUALITY. 22. Although the investigation into structure, and the consequential qualities of the organs, is more restrictively the object of anatomy ; yet the precise definition of their various distinctions is of importance to descriptive entomology. We must not, therefore, omit defining orismologically these peculiarities of the structure of the parts, and the more so, as they are chiefly superficial. Under this head we shall accordingly treat particularly of the differences of substance, and of those of superficies, excluding however from this chapter those arising from individual substances springing from, or reposing upon the surface of bodies, such as hair, scales, &c. &c. 23. Differences of Substance. MEMBRANOUS (membranaceum), is a delicate, flexible, transparent, thin, superficially distended substance. CORIACEUS (coriacenm), is also a thin, flexible, distended substance, but is somewhat thicker, and opaque, resembling leather. CORNEOUS (corneum), a thicker, harder, entirely opaque, and scarcely flexible substance, resembling horn. CARTILAGINOUS (cartilagineum}, is a substance combined of the qualities of membrane and horn ; it is thicker than the latter, but somewhat transparent, flexible, and always whitish. SOLID (solidurri), is a substance consisting of one mass, with no vacant interstices. POROUS (porosuni), when small interstices or holes are observable upon the surface. SPONGY (spongiosum), when soft and intersected by small channels throughout its substance. TUBULAR (tubulorum), when a longitudinal cylindrical body is hollow throughout its whole length. VENTRICOSE (ventricosum), when this tubular pipe suddenly distends into a large cavity. FLEXIBLE (flexilis), a substance possessing elastic properties. RIGID (rigidum'), when it will not bend without breaking. GENERAL ORISMOLOGY. 17 24. Differences of Surface. SMOOTH (lave), a surface without either impressions or elevations. LEVIGATE (Icevigatum), a smooth surface, somewhat shining. SHINING (nilidum, politum), when a smooth surface reflects, as if formed of metal. LUCID (lucidum), possessing this quality in a high degree, reflecting with the brilliancy of a mirror. SCABROUS (scabnmi), a surface covered with small and slight elevations. ROUGH (asperurri), when these elevations are more perceptible. VERRUCOSE (verrucosum), a surface beset with large smooth ele- vations, resembling warts. TORULOSE (torulosurri), when there are but few elevations spread about, but these of considerable size. GRANULATED (granulatuni), when small roundish elevations are placed in rows ; MURICATE (muricalnm), when dispersed elevations rise in sharp points; ECHINATE (echinatum) , when they rise higher, and are thinner ; CATENULATED (catenulatum), when longitudinal eleva- tions are connected like the links of a chain, and are placed in rows ; INTRICATE (intricatum), when the elevations and depressions are placed without any regularity, but close to each other ; PAPILLULATE (papil- hilatuin), when the dispersed elevations or depressions have a smaller elevation in their centre. LINEATE (lineatum), when there are fine longitudinal elevated lines ; COSTATE (coslatum), when these lines are stronger, and the intervals between them wider ; FURROW (sulcus), is such an interval. TESSELATE (tesselatum), when the lineate surface is intersected by similar transverse elevated lines, as it were chequered (it is also used to indicate square scales); RETICULATED (reticulatum), when the stronger lines intersect each other like the meshes of a net. STRIATED (striatum), when there are parallel longitudinal shallow impressions; SULCATE (sulcatum], when these impressions are broader and deeper than the preceding, or rather when they are of the same width as the interstitial elevations ; whereas, when striate, these inter- stices are much wider ; PORCATE (porcatum), on the contrary, when the sulcations are deep, and very much broader than the intervening c 18 GENERAL ORISMOLOGY. elevated ridges ; CANALICULATE (canaHculatinii), is a surface, which has in its centre a broad, but not very deep longitudinal furrows ; EXARATE (e.raratum), when several such furrows with perpendicular margins, and wide, elevated intervals, run parallel to each other ; ACICULATE (aciculatum}, when many fine, frequently undulating striae running either parallel, or interweaving each other, make the surface appear as if scratched with a needle. PUNCTURED (punctatum} , a surface covered with small impressed punctures; VARIOLUS (varioloruin), when larger depressions are iso- lated, and resemble the maiks of the small-pox; FOVEOLATE (foveo- lalum), or SCROBICULATE (scrobiculatum], when somewhat deeper impressions become narrower towards their bottom ; CLATHRATE (clath- ratum), when such foveoles are placed in rows, having elevated longitu- dinal lines between them ; FAVOSE (favosuni), when these depressions stand close together, so that the surface resembles a honey-comb ; ENGRAVED (ejcsculptuvi), when a variety of irregular longitudinal depressions cover the surface; VERMICULATE (vermicrilatum}, when the depressions are longitudinal and tortuous, like a Avorm-eaten stem. The following distinctions are made with respect to the convexity or concavity of a surface : PLANE (planum^, when the whole surface is of an equal height. CONVEX (convexinn), when a surface 'rises gradually to its centre, which becomes thus the highest of the whole. CONCAVB (coticavum), when the surface gradually declines towards its centre, thus becoming the deepest. EXCAVATED (excavatum), a depression, the section of which is not the segment of a circle. GIBBOSE (gibbosum), when separate parts rise higher than the rest; GIBBOUS (gibbum}, on the contrary, is a surface, the section of which is not the segment of a circle; TUBERCULATE (tuberculatum), when the whole surface rises conically; RUGOSE (rugosum), when longitudi- nal elevations are placed irregularly like coarse wrinkles. The inequalities, caused by a production of the true surface, are thus distinguished : ACULEATE (aculeatum'), with slender pointed processes ; SPINOSE (spinosu-ni), covered with solitary, thicker, and frequently bowed pro- cesses. UNARMED (mut'icum, inertne), when no such processes exist. The first word is generally used when terminal processes are wanting, where they are usually present. ()Kisi\roLo<;-\ , 19 III. CLOTHING. 25. Having thus explained the differences of surface produced within itself, we have yet to notice those caused by individual substances lying upon or attached to it. GLABROUS (glabrum), is a uniform surface, without this distinction, when according to rule hair Qz7z) clothes it. PILOSE (pilosum), when covered with dispersed, somewhat long and bent hairs. HAIRY (hirtum, hirsutum), when densely covered with short stiff hairs. VILLOSE (villosum), when densely covered with long slender hairs, which rise upright. PUBESCENT (pubescens), when the hair is soft, short, and decumbent. CRINITE (crinitum), when the hair is very long, slender, and dis- persed. SERICEOUS (sericeum, kolosericeum) , when short shining hairs lie closely to the surface, resembling silk or satin in splendour. LANUGINOSE (lanuginosum), when longish curled hair is dispersed over the surface. TOMENTOSE (tomentosum) , when longish curled hair stands densely and interwoven. SETOSE (setosum), with dispersed long stiff hair. CILIATE (ciliatum), when fringed with short stiff hair. PINNATE (pinnatum), when stiff hairs, or thorny processes, occupy the opposite sides of a thin shank. SQUAMOSE (squamosum), when covered with small broad scales which lap over each other ; such a scale with a short stalk is called squama. When these scales are square the surface is called TESSELATED (tesse- iatum\ PRUINOSE (pruinose}, when covered with minute dust, scarcely discoverable by the lens ; FARINOSE (farinosum'), when the dust is more perceptible, resembling flour, and removed by the least touch; POLINOSE ( polinosurnj, this dust, when yellow, like the pollen of flowers ; PUL- VERULENT (pulverulenittm), RORULENT (rorulentum), express very similar, scarcely precisely distinguishable qualities ; LUTOSE (lutosuni), apparently or absolutely covered with dirt *; NAKED (nudum], a surface without either a scaly or dusty covering. * Many beetles that live upon a clay soil are always thus covered with dirt; for the sppric diate legs of the male of Anthophora retusa). IV. COLOUR. 27. Colour succeeds to form, and the various qualities of surface, as the next most important character for distinguishing insects. Even in groups where colour cannot be used as a specific character, from its great and frequent variation in the same species (as Coccinella varia- bilis, Illig.), it then becomes important to notice precisely its differences for the requisite separation of the varieties of the species. In order to explain distinctly these differences of colour, terms expressive of the mul- titudinous gradations of tint produced by the various admixture of the several primary colours are necessary. But as we have not yet arrived at a general unanimity, which may be readily perceived by the comparison of the descriptions of the same insect by different authors, it is vain to hope that we shall here solve the problem of reducing the system to universal harmony. Clearly perceiving these difficulties, Lamarck, and after him Latreille*, proposed a peculiar method for the definition of colour, whereby he thought he had removed every possible doubt. * P. A. Latreille, Ilistoire Naturelle des Crust, et des Insectes. Paris, an. XII. Vol. i. p. 331, &c. GENERAL ORISMOLOGY. 21 He considered three of the seven prismatic colours as simple primary colours ; viz. blue, red, and yellow, and adopted them as the basis of his whole system, seeking their correspondent affinities in nature. Blue conducts on the one side to black, yellow to white. From the admix- ture of equal parts of the approximate colours, two new ones arise ; viz. violet, from blue and red, and orange, from red and yellow ; green is excluded, it being treated as the unnatural and irregular union of two colours removed from their true places (!). Thence we have the fol- lowing series : Black, blue, violet, red, orange, yellow, white. This series he inscribes upon a scale, divided into sixty equal parts ; he places white at 0, and proceeding from 10 to 10, consecutively arranges them all. The modification, in the union of two approximate colours, is determined by their relative numerical power ; for example, five parts black, and five blue, give black-blue ; eight parts black, and two blue, give a very deep black-blue (bleu noir triple), &c. By this means, he obtains sixty different gradations of colour, which, we admit, frequently suffice for the description of natural colours, but do not cer- tainly extend to all, for all unions of black and red, red and white, black and white, are wanting. This table is also rendered excessively defective by the entire omission of green, one of the most prevailing colours, and in the most variable gradations, throughout nature. 28. Eight primary colours are generally adopted in Natural History ; viz. white, grey, black, brown, red, blue, green and yellow. Each of these colours admit of being mixed with others, and even some of those named are produced by the union of two of the rest. It is, therefore, evident, how excessively variable must be the effect of such mixtures of colours, and how very closely they approach to and pass into each other, so that the precise distinction of each change would be an ungrateful and useless task. The degrees and intensity of colour are also very variable. The following terms are in use to express some of them : DEEP (saturate), when colour is very intense or thickly laid on. PALE (dilute), when but slightly coloured. BRIGHT (Icete), when the colour is clear and vivacious. FADED (obsolete), when it appears as if faded by the air. SORDID (sordide), when the colouring is impure, and as if clouded by the admixture of another. 22 GENERAL ORISMOLOGY. 29. WHITE (albus), a pure plain white. NIVEOUS (niveus), the purest, dazzling white of snow. LACTEOUS (lactens), white, with a bluish tint like milk. CRETACEOUS (cretaceus), white, with a yellowish tint like chalk. 30. GRISEOUS (griseus), a mixture of black and white. HOARY (canus, incanus), grey, with the white prevailing. CINEREOUS (cinereus), a dark grey, in which the black prevails. MOUSE-COLOURED (murinus), grey, with a yellowish tint. FAWN-COLOURED (cervinus), grey, with a reddish-brown tint. SMOKY (fumatus), grey, inclining to dark-brown, like the colour of smoke. 31. BLACK (niger), pure black, the colour of fresh garden-earth. BLACKISH (nigricans), a bright black, inclining to grey. ATROUS (ater, aterrimus), the purest, most intense black. COAL-BLACK (anthracinus), a deep shining black, with a bluish tint. PICEOUS (piceus), a bright black, with a greenish tint. 32. Fuscus (fuscus), dull brown, a plain mixture of black and red. BROWN (brunneus), a pure bright brown. CHESTNUT (caslaneus), a bright red-brown, the colour of the fruit of the horse-chestnut. BAY (badius), a clearer lighter brown than the preceding. FERRUGINOUS (ferrugineus) , a brown, wherein red prevails, resem- bling the rust of iron. FULIGINOUS (fuliginosus), a very deep dark broAvn, the colour of soot. UMBER (umbrinus), a bright dark brown,' with some yellow FULVOUS (fulvus), a light brown, with much yellow. 33. RED (ruler'), the usual red ; the colour of burnt tiles. MINIATOUS (miniatus), the colour of red lead. LATEIUCEOUS (lalcricius), the yellow-red of yellowish bricks. GENERAL ORISMOLOGY. 23 SANGUINEOUS (sanguineus), a deep red, with a dash of blue, the colour of fresli blood. PURPLE (purpureus or jjuniceus), a bright red, with a violet tint. 34. BLUE (cyaneus), pure dark blue of Indigo. AZURE (azureus), a clear brilliant blue, viz. wings of Lycaena. SKY-BLUE (cdBtruleus) a pale blue, like the colour of the sky. VIOLET (violaceus~), a blue, with a reddish tint. PRUINOSE (pruiniis, pruinosus}, a reddish blue, with a whitish covering, like the bloom of ripe plums. GLAUCOUS (glauciis}, a bright blue, with a strong admixture of white, inclining to grey. C^ESIOUS (ccesius,') a greenish, grey, sordid blue. DARK-BLUE (atroceruleus), a dark, deep blue, inclining to black. 35. YELLOW (Jlavus}, most beautiful, and purest in the colour of sulphur, thence sulphureous (sulphureus) . STRAMINEOUS (slramineus) , a pale, less brilliant, but pure yellow of the colour of straw. SAFFRON-COLOURED (croceus), or ORANGE (aurantiacus), yellow, with an admixture of red. OCHRACEOUS (ochraceus), a similar but sordid yellow, inclining to brown, the colour of ochre. LUTEOUS (luteus), a brownish yellow, the colour of clay. LURID (luridus), a dirty yellow, more inclining to brown. LIVID (lividus), a palish yellow, with a blue tint. TESTACEOUS (tcstaceus), a dull, yellow brown. 36. GREEN (viridis), the mixture of blue and yellow, the prevalent colour of the leaves of plants. (ERUGINOUS (ceruginosus), a bright green, inclining to blue. PRASINOUS (prasinus'), a light green, inclining- to yellow. OLIVACEOUS (olivacens^, a green, Avith an admixture of brown. YELLOW-GREEN (faivo-vircns'), a bright green, with the yellow predominant. 24 GENERAL ORISMOLOGY. 37- Besides the above terms, expressive of colour, several are used derived from natural objects, or from those in daily use. HYALINE (hyalinus), expresses a transparent, colourless part. PELLUCID (pellucidus, diaphanus), a coloured but transparent part. OPAQUE (opacus), a clouded, not transparent part. The brilliant or glittering colours are derived chiefly from metals or other minerals, to which they are exclusively peculiar. OPALINE (opalinus, or opalissans), the prismatic reflection of the opal. MARGARITACEOUS (marg'aritaeeus\ reflecting the prismatic colours like mother of pearl. CRYSTALLINE (crystallinus), the pure transparency of crystal. AMETHYSTINE (amethystinus), the brilliant colour of the amethyst. SMARAGDINE (stnaragdinus), the brijliant green of the emerald. SILVERY (argenteus') , the metallic white of silver. GOLDEN (auratus, or inauratus), the metallic yellow of gold. AURICHALCEOUS (aurichalceous ), the metallic yellow of brass. CUPREOUS (cupreus), the metallic red of copper. ./ENEOUS (ceneus), the green metallic colour of bronze. CHALYBEOUS (chalybeus), the metallic blue of case-hardened steel. PLUMBEOUS (plumbeus), the pale blue grey of lead. FERREOUS (ferreus), the metallic grey of polished iron. SPLENDENT (splendens) , any colour having a metallic splendour. 38. There are also peculiar terms to express the painting of parts. SPOT (punctum), a small roundish dark spot upon a plain surface ; these spots must be distinguished from impressed punctures, but the latter are sometimes differently coloured from the rest of the surface. ATOMS (atomi), are points not proceeding from the colour of the surface, but applied to the surface ; they must, however, be so large and distinct that each can be clearly recognised. PUSTULE (pustuld), a point of larger circumference. MACULA (macula), is a tolerably large angular spot, of a dark colour, upon a uniform surface. GUTTA (gulla), is a light spot upon a light ground, viz. white upon yellow. GENERAL ORISMOLOGY. 25 LITURA (litura), an indistinct spot, paler at its margins. PLAGA (plaga), a longish spot of irregular form. LINE (linea), a very slight, generally straight, but also sometimes gently bent, differently coloured stripe. VITTA (viita), a broad longitudinal stripe. STRIGA (striga), a transverse band. FASCIA (fascia), a broad transverse band. ANNULET (aimulus), a narrow differently coloured circle upon a surface, or upon the circumference of a part. LUNULET (lunulct), a half-moon shaped spot of a different colour. OCELLUS (ocellus}, a coloured ring, with a similarly or differently coloured centre. In the latter case this point is called the PUPIL (pupilla), and the space between it and the ring the IRIS. From these terms are derived the adjectives of a similar signification, as Elytra vittala, &c. Besides these, many adjectives are used to express similar, but less peculiar painting, such as, IRRORATE (irroratus), when a space is covered with the above described atoms. NEBULOSE (nebulosus), when a surface has different, lighter and darker and paler markings resembling the irregular colouring of a cloud. SIGNATE (signatus, or notatus), is a part with distinct markings. DISPERSED (adspersus, conspersus), when these markings consist of small spots standing close together. FENESTRATE (Jenestratus), is a dark surface, with one or more transparent spots. MARMORATE (marmoratus) , when the markings are variegated like marble. TESTUDINATE (testudineatus), when the surface resembles the back of a tortoise. UNDULATE (imdulatus), when the markings are waved either longitudinally or transversely. UNICOLOR (wm'co/or), a part uniformly coloured. CONCOLOROUS (concolor), when resembling in colour to any other part of the same insect. VERSICOLOURED (versicolor), when a part displays several different colours, indeterminately restricted. DISCOLOURED (discolor), when the same part of an insect has diffe- rent colours. (For example, legs are called discoloured when the anterior are red and the posterior black.) IRIDICOLOR (iridicolor), a surface reflecting the prismatic hues. 26 GENERAL ORISMOLOGY. V. MEASURE. 39. A universally known measure, the Paris line, the twelfth part of an inch, has been adopted as unit for the determination of the length of insects. This character is of considerable importance from the very constant uniformity of size, not only of the parts of the same individual, but also of all the individuals of the same species* ; and thus the length of every possible part can be as precisely ascertained as the purpose in view may require. This mode of measuring has by far the advantage, and must consequently never be omitted when a s pecies is named and published. The difference of size which imme- diately catches the eye is frequently the first best character whereby we are enabled, at the very first glimpse, to separate two, or more, closely related species. 40. Besides this universally applicable, absolute measure, there is another relative one. A portion of the insect is adopted as the unit, and by means of it, the length of the remainder is determined, or two or more parts are compared together, and thereby a proportional rela- tion formed. This plan is also useful particularly when given in con- junction with its absolute length. The folloAving is the mode of proceeding to the precise determination of the longitudinal pro- portions. We must commence by measuring the whole length of the body and giving it, and then the length and breadth of the different di- visions must be placed as in the following table : HEAD. THORAX. ABDOMEN. Length. Breadth. Length. Breadth. Length. Breadth. 0,70 1,0 1,80 2,10 3,50 2,40 Such a table immediately gives the relative proportions of each ' This is liable to innumerable exceptions, but a familiarity with insects soon gives an idea of the range that it may be allowed, as it varies considerably in different species. It can never be permitted alone to determine a difference, unless supported by other cha- racters which, in themselves, sometimes (particularly in colour) would scarcely suffice for a separation. Its use is consequently of importance for identification, exclusive of its value in determining the effects of climate and temperature. TR. GENERAL OKISMOLOGY. 27 chief division to the other ; and it is very easy, by a comparison with these, to indicate sufficiently the length of the limbs ; as, for example, we might say of the antennae, as long as head and thorax together ; or of the wings, they are one-half longer than the abdomen. And the length of the legs, and their several joints, may also be thus shown. Hausmann* was the first, as far as we are aware, who applied this method to insects, and A. Ahrens followed him, and which all writers of Monographs should likewise do. But it can scarcely be adopted in a complete system of insects (the want of which is now so strongly felt upon all sides) by reason of its too great prolixity. In such a work, the mere length must suffice, but which must never be omitted. 41. This precise and elaborate measuring of the parts has been endea- voured to be dispensed with by the introduction of a comparison with universally known objects. The width of the thumb (an INCH, pollex^) has served for the determination of the length of large individuals. Half that length is indicated by the adjective HALF (dimidius), which is universally used to indicate half the size. We thus say half as large, dimidio minus; by one-half larger, dimidio majus ; by one-half broader, dimidio latins, &c. In the same manner the comparative numerals are applied, triplex, quadruplex, &c. Thus, one-third as large, triplo-minus ; three times as large, triplo-majus ; one-fourth as large, quadrtiplo-minus ; four times as large, quadruplo-majus. Quincuplex and sexluplex, are also, but very seldom, used. 42. EQUAL size is indicated by the adjective ezqualis ; a more con- siderable size is given generally without precise determination, or by the expressions superans and excedens. Very variable size, as well as the variableness of colour, are indicated by the words variabilis, mutabilis. * Illigcr's Magazine, vi, 229. t Neuc. Schreftcn der Hallis. nuturf. Gesellschaft, i. 3. 28 GENERAL ORISMOLOGY. VI. AFFIXION, DIRECTION. 43. We have but few generalities to give upon affixion and direction, insects having but few exterior organs, and those applied in a uniform manner to the same place. But there are a few phenomena of greater universality, which we shall now refer to. 44. Affixion is of a double kind. ADNATE (adnatuiri) are those parts which form an immediate continuation of the base upon which they repose, and are besides immoveable. ARTICULATE (arliculalum), are those parts which stand in connexion with the body merely by a flexible membranous medium, as sinews, &c., and possess a greater or less degree of motion. Processes such as SPINES (spince, aculei] ; HORNS (cornua), or plainly processes, forms, merely distinguished from each other by then- size, and often indifferently applied, require no general notice of their affixion, it being precisely the same in all. In the ARTICULATION (articulatio}, we distinguish the ball and socket (Arthrodia), whereby motion is possible in every, or very many ways (for example, between the head and prothorax), and the gynglimous (gynglimus}, which admits merely of the flexion and extension of the two united parts. 45. With respect to the direction of parts, we distinguish ANTERIOR (anticuiii), lying near the head. POSTERIOR (posticum'), that approximate to the end of the body. SUPERIOR (suprci), placed upon the back. INFERIOR (infra), attached to the ventral portion of the body. BOTH SIDES (utrinque), indicates a quality or peculiarity found on each side of the body, and indeed at the same place. BASAL (basales), are parts or organs arising from the base of another. TERMINAL (terminalis], such as arise from its apex or end. AXILLARY (uxillares), are those which spring from the point of union of two others. GENERAL OK ISMOLOG Y. 29 ERECT (erectus), a part which stands perpendicular upon another. ADUNCOUS (aduncus), a part which gradually bows from the direct line. NUTANT (nutans), a perpendicular part, the apex of which bends over. DEPRESSED (depressus), a part which appears to have been pressed from above. COMPRESSED (compressus) , on the contrary, when the pressure seems to have been made from the sides. REFLEXED (reflexus, reclinatus), when the margin of a part rises upwards ; DEFLEXED (deflexus), when it bends downwards. REVOLVED (revolutus), and INVOLVED (involutes), are also thus distinguished, but they indicate a greater degree of it an absolute rolling up. COMPLICATED (complicates), is a part laid longitudinally in folds ; REPLICATE (replicates), when the apex bends round, and the part is thereby refolded. A part prolonged or distended most considerably from front to back, is called STRAIGHT (reclus) ; when its greatest distension, however, is at right angles with the length of the body, it is called TRANSVERSE (transversus). Note. Many of the general terms of other writers, of Kirby, for instance, are passed over, as their signification may be found in any Latin dictionary. THIRD CHAPTER. PARTIAL ORISMOLOGY 46. HAVING thus concluded the examination of the general differences observed in all, or the majority of the organs, it now remains for us, as the subject of the following chapter, to describe the insect body in its separate periods of existence, and all the thence perceptible differences of its various organs. The illustration of its several stages of develop- ment first claims our attention. 47. Commencing our investigation with the first beginning of insects, we may lay it down as a universal law, that all insects originate from EGGS (ova). With the exception of the few instances, wherein the egg is hatched in the body of the mother, and the young thus born more fully developed, a species of propagation to which the ancients applied the name of Insecta ovo-vivipara (Musca carnaria, &c.), all insects are truly animalia ovipara. We must here indeed mention a second exception, comprising those Diptera which are retained in the body of the mother, until transformed into pupae, and are excluded in an apparent egg-shell, but which is, in fact, the pupa-case. This species of developement is peculiar to a single family, which has thence received the name Diptera pupipara. Exclusive of these very rare anomalies, we may observe four distinct periods of existence in every insect, namely, those of the EGG, the LARVA, the PUPA, and the IMAGO, or PERFECT INSECT. In each of these states they are subject to manifold differences, arising from the various groups to which they belong, and to the contemplation of which we now pass. PARTIAL ORISMOLOGY. 31 I THE EGG (Ovum). 48. The shape of the egg in the several classes of animals is in general so exceedingly uniform, that a peculiar expression has been thence deduced for its definition. Indeed, in the class of insects, the majority of eggs are OVAL (ovafe) ; but their shape is subject to so many differ- ences, that it is necessary to enumerate the chief. Perfectly GLOBOSE (globosum) they are very frequently, particularly in several families of Lepidoptera. SEMIGLOBOSE (semiglobosum), likewise in several Lepidoplera ; for example, in Harpy a vinula (pi. i. f. !) CONIC (conicuiri) also among Lepidoptera, as in Pontia Brassicee (pl.i.f.2) CYLINDRICAL (cylindricum), chiefly in such insects which lay them in numbers, and close together (Gastrophaga Neustria, pi. i. f. 3). LENTICULAR (lenticular e), depressed, circular, and frequently ribbed eggs, as in the moths (pi. i. f. 6). Other forms are TURBAN-SHAPED (tiaratum, pi. i. f. 11); MELON- SHAPED (cucurbitaceum) ; PEAR-SHAPED (pyriforme) ; BARREL- SHAPED (pi. i. f. 5). Many eggs are placed upon long, straight (Hemerobius perla, pi. i. f. 14), or shorter, bent (Ophion luteus, pi. i. f. 16), footstalks, and are thence called PETIOLATED (ova petiolata). Others have atone end par- ticular appendages; for ex. the EARED-EGGS (ova aurita, pi. i. f. 17) of Scatophaga putris, which, just before their apex, are furnished with two short oblique appendages, that they may not sink too deep in the matter whereon the insect deposits them ; or CROWNED (ova coronata, pi. i. f. 19) of the water scorpion (Nepa cinerea), which are surrounded at their superior extremity with a circle of strong spines, for the reception of the following egg, whereby they hang in a row together, and do not inaptly represent the small, short-limbed branches of the horse- tailed grass (equisetum). 49. With respect to the surfaces of eggs, they are generally smooth (o. glabra], but also frequently uneven, or covered with a variety of regular sculpture. Some are provided with lateral wings (ova alala) ; 32 PARTIAL ORISMOLOGY, others with short ribs extending from one pole to the other (ova costctta, pi. i. f. 5)j others with delicate filaments, which show the segments of the embryo * (Attacus paphia). Other eggs display upon their surface cross lines and sculpture, which gives them a reticulated appearance (ova reliculata), Hipparchia Hyperanfhus (pi. i. f. 13) ; in others these lines take a curve, so that the egg appears as if covered with tiles (Hipp. Jurtina) ; others, lastly, have decided knobs, making the surface rough and uneven (Pont. Brassicte). We also occasionally observe in eggs irregular wrinkles and impressions, but which do not proceed from the sculpture of the superficies, and are accidental, arising from their drying after being laid. The colour of the eggs of insects is, notwithstanding their great variety, not so variable as in the class of birds. White, yellow, and green, are the chief colours, indeed almost the only ones ; for the few others, as brown in Harp.vinula, or green (Cimex baccarum), or banded (Gastr. querci folia, p. 1. f. 1), import but little, considering the greater universality of the before -mentioned colours. We occasionally observe very dark ones, even a black brown (Culex pipiens) . 50. It is also interesting to observe the way in which the eggs are deposited. Some lie solitary, and dispersed upon the plants and shrubs which nourish the young (ova solitaria.') Others, which are deposited within the substances, which serve the young as food, are called (ova imposita) ; for ex. the eggs of the Ichneumons in the bodies of caterpillars. The eggs of Gastr. neustria are placed in a spiral line around the young shoots of the plant that feeds the caterpillar (ova spiraliter deposita, p. 1. f. 15) ; others form irregular heaps, which the mother secures from cold, and other prejudicial influences, by means of the hair of her body (ova pilosa, p. 1. f. 4), for ex. Liparis chrysorrliea,fascelina, dispar ; others again are concealed in lumps of dung (ova glebata, for ex. Gymnopl. pilnla- ritts) ; others are formed in the galls of plants (gallce), occasioned by the punctures of the mother (ova gallata, for ex. Cynips, Diplolepis, Trypeta) ; many, lastly, are placed in close cells formed by the parents for this purpose (ovafavosa, for ex. Apis, Vespa, Pelopceus). All these eggs adhere by a peculiar gummy secretion, and are thence called ova * Lin. Tr. vii. 3-1. THE LARVA. ;J3 gummoxa ; but such eggs as lie dispersed in any substance, as, for ex. the eggs of the house fiy (Mitsca domestica),in dung, are called naked (ova 7iuda). Besides those above indicated, there are many other differences, with respect to their mode of being deposited, which, as they are peculiar to certain genera or families, we can take notice of only in the natural history of such groups. II. THK LARVA. (Larva.) 51. As soon as the young insect breaks through the egg-shell, it is called either LARVA, CATERPILLAR, or MAGGOT. In this state it frequently appears in the shape of a long, more or less cylindrical, ringed worm, either apparently without a head and feet, or having a head only, or else provided with several (at least six) feet. In other, but less numerous instances, the young assumes the form of the parent, although necessarily much smaller, and always destitute of wings, whether the parent insects possess them or not. Both kinds of metamorphosis thus evidently differ considerably from each other from the mere form of the young itself ; and in the progress of their development this difference becomes still more perceptible ; for whilst, in the latter instance, the young one gradually attains both the size and perfect form of its parents by a frequent change of skin only, in the former species of development we observe, also after successive changes of skin, a state of repose, in which the insect neither takes food nor, in the generality of cases, moves a period of its life distinguished by the name of PUPA STATE ; and at the completion of this stage of its existence only, is it that the PERFECT INSECT, or IMAGO, bursts forth in all its beauty. It was in reference to the actual differences of these modes of development, that the names were applied which are used to distin- guish them. Taken collectively, they are called METAMORPHOSES ; the application of which name may, doubtlessly, be justified by the decided dissimilarity of the same individual insect in its several stages of exist- ence. The last kind of metamorphosis is called COMPLETE (metamorph. completa), because in it alone there is a true metamorphosis of the individual; the former, on the contrary, is called INCOMPLETE (m. incomplete.), since in it there is, properly speaking, no change of form, but merely a repeated casting off of the exterior skin. Although these terms are strictly derived from the condition of change, other writers, Fabricius for instance, have had different views. D 34 PARTIAL ORISMOLOGY. The names he proposed for the, according to him, several kinds of metamorphoses are the following : COMPLETE (m. completa) is, according to him, that species of change wherein the larva is formed exactly like the perfect insect. It is found only among such as are destitute of wings in their perfect state (e. g. Pediculus, Cimex). SEMI-COMPLETE (m. semi-completa), when the young resembles the parent with respect to form, but is as yet deficient in the wings peculiar to the latter. INCOMPLETE (in. incompleta), when the young creeps from the egg as a maggot, and the pupa has free, distinct limbs, although quiescent (Hymenoptera, Coleoptera). OBTECTED (in. obtecia], is the change only distinguished from the latter by the limbs, as well as the body, being enclosed in a hard corneous case, upon which their form and position are strongly indicated (Lepidoplera}. COARCTATE (m. coarctato} he calls, lastly, that change wherein the larva is a maggot without legs, and the pupa is enclosed within a round, almost egg-shaped, corneous case, upon which there is not the least indication of the parts of the perfect insect. In opposition to this apparently very precise distinction of the different kinds of metamorphoses, we may object that many cases occur which will not admit of being arranged under any of those heads ; for example, the larva of Xylophagus is without feet, and yet the limbs of the perfect insect are perceptible upon the pupa case ; it is the same with the genus Stratiomys ; and again, a footless maggot is trans- formed into a pupa with free limbs, as in Ichneumon. Exclusive of these considerations the idea of a complete change is most strictly appli- cable to what Fabricius terms incomplete, and his most complete, on the contrary, being evidently the most incomplete. It consequently appears to us preferable to adopt but two chief kinds of metamorphoses, as, as we have seen, between the several subdivisions, very many connective and alternative conditions exist. 52. The larvae of insects with an imperfect metamorphosis, are to be recognised in general by their want of wings and scutellum ( 76) with the exception of the few instances wherein the perfect insect has no wings. In such cases certainty can be derived only from their relative size in knomv species, as the larvae are invariably smaller than the THE LARVA. 35 imago. In other respects, they wholly agree with their parents as regards their conformation ; the same orismology consequently applies to them as to the latter, and with which we shall become acquainted in the description of the perfect insect. 53. All larva; with a perfect metamorphosis have a long, generally cylindrical body, composed of thirteen more or less distinct rings or segments*. Many, which have neither a distinct head, nor feet, are called MAGGOTS (PI. II. f. 1) ; in others the head is clearly distinguished, but the feet are wanting (PI. II. f. 3) ; others again, in addition to the head, have six feet, which are placed upon the three first segments of the body following the head these are called LARVAE (PI. II. f. 4. 6) ; others, lastly which are called CATERPILLARS (Erucce), possess, besides the six horny legs of the three first segments, several membranous legs, called PROLKGS, upon the ventral and anal segments (PL II. f. 5, 7-12). The portions of the body of larvae, consequently, which chiefly merit our attention are, the HEAD, the BODY, with its various clothing, and the LEGS. The HEAD (capiit) always occupies the first of the thirteen seg- ments of the body. In many cases it does not at all differ from the other divisions of the body, and is, like them, covered with a soft skin, and equally flexible and changeable in its form. This conformation ' With respect to the number of the segments, the text might create a little confusion ; for Burmeister says, at 57, in rather an obscure passage, as it does not clearly define whether he includes or excludes the head, that it consists of twelve segments ; thus contradicting what he has previously said above; and Ratzehurg*, in a paper upon the apodal larvae of the Hymenoptera, figures them generally as consisting of thirteen segments, which is their true number, the first and second of which become the head, the third, fourth, and fifth, the thorax, the sixth the pedicle, seventh to thirteenth the abdo- men ; but, at fig. 43, he represents the larva of Apis Mellifica with fourteen segments. Whether this arise from his having figured the larva of the male of that insect, I do not know, for the text does not elucidate it ; but the accompanying figure (44) appears to be the pupa of the male, as it has seven segments to the abdomen. I am not aware that it has been before observed, that the larvae of the males of the aculeate Hymenoptera will necessarily have an additional segment. Ratzeburg seems to take great merit to himself for having discovered that the larva of the Hymenoptera are headless, as he says, and seems to insinuate a censure upon Swammerdam, Reaumur, De Geer, Kirby and Spence, Latreille, &c., for not having noticed as much. It is evident that these writers considered the two first segments as the head, and justly ; for although as yet destitute of the usual organs, they were in fact the head, only requiring further development TR. * Nov. Act. Med. Phys. Acad. Ca-s. Leop. Carol. Nat. Curios, t. VIII., pi. i. p. 145. D 2 30 PARTIAL OKISMOLOGY. of the head occurs only in the maggots, which are destitute of all the organs observable in the heads of caterpillars, such as antenme, eyes, &c. ; but there are to be seen, in the anterior opening which forms the mouth, two horny bristles, which seem to represent the mandibles, which serve for the destruction of its prey, when, for instance, the maggot feeds upon other insects. In larvae and caterpillars, however, the whole head is covered by a peculiar corneous case, which is divided into two by a perpendicular suture descending from the vertex, and separating in a fork just above the mouth. The general form of this covering is more or less round, resembling a hemisphere ; in many instances it has a triangular, and often a complete heart-shaped figure ( Sphinx Ligusl.ri, Smerinthus Popu/i, and many others); sometimes each half is produced at the vertex into a pyramidal process (Apatura Iris, PI. II. f. 16), or the whole superior part of the head is completely covered with thorns and spines (Limenitis Amphinome, PI. II. f. 15). As peculiar organs of the head of larvae, we must notice the oral apparatus, the antennae, and the eyes. All true caterpillars have mouths adapted to manducation, as have also all larvae with horny legs, and, indeed, many without legs. The mouth is discoverable at the anterior or inferior contracted portion of the head ; it is formed by the Mat, longitudinally quadrate ( sometimes taking the shape of a segment of a circle) corneous upper-lip, or LABRUM (labrum, PI. II. f. 13, ) ; the equally strong corneous, horizontally-moving- upper-jaws, or MANDI- BLES (mandiiiulas, PI. II. f. 13, A, b) ; the weaker, but very similar, under- jaws, or M AXILLAE (rnaxillce, c, c), with their feelers, or PALPI (palpi), and the likewise flat, more or less triangular, horny under-lip, or LABIUM (labium, d), which also is very generally furnished with short FEELERS, or palpi; and this under-lip, or labium, closes the mouth from below, as the labrum does from above, whilst the closed mandibles completely shut the orifice in front. All these organs are also found in the perfect insect, and we shall consequently describe them more in detail when we arrive at that stage of its existence. The ANTENNA (antenna, f, f) are placed near the mouth, at the base of the mandibles and maxillse. In larvae they consist of but few, generally but three joints, or short narrow corneous cylinders, united together by a delicate skin. They are always of a bristly or filiform shape, even when the antennae of the perfect insect are very differently constructed ; for in caterpillars they present themselves as very short conical processes, while in the butterflies, which proceed from them, the antennae are very long, and many-jointed. HIE LARVA. 37 Many larvae are destitute of eyes, namely, all maggots with an undeveloped head, as well as many larvae with a distinct corneous head-plate. The eyes of larvae are always simple, and perfectly agree in form with those eyes of the perfect insect, with which we shall become acquainted as ocelli. They are also placed in the vicinity of the mouth, close behind the antennae (g, g) ; they vary in number from one to six on each side ; but the caterpillars of butterflies appear invariably to possess the latter number 54. These, as well as the larvae of the saw-flies (Tenthredonodea and Urocerata,) and those of the May-flies (Phryganeodea), possess, attached to their maxillae, a peculiar organ, which Kirby and Spence very aptly call a SPINNERET (fusulua, PL II. f. 14), which is of great importance to them for the preparation of their cocoon. It originates from the anterior portion of the labium, and is a slight tube, obliquely truncated at its apex, and composed of several alternately corneous and membranous slips. It is through this tube that the clammy liquid passes, which has been secreted by two glandular organs for the pre- paration of the silk, and which can be spun into thicker or thinner filaments at the will of the caterpillar, by the power it possesses of distending or contracting the cavity of the tube. The larvae of some Coleoptera and Dictyoloptera, which also spin cocoons, do not, however, possess this organ ; but the silk is produced by an apparatus at the anus : a very different construction must consequently obtain in them. 55. The head is immediately succeeded by three segments, which ulti- mately, in the perfect insect, form the thorax. They are recognised in many larvae by the short, corneous, articulated and conical feet, which are observed only upon these segments. In general they are con- structed like the rest; but in the larvae of many Coleoptera, particularly of the superior families, they are distinguished by a peculiar conforma- tion ; their exterior integument is corneous, like that of the head, whilst that of the abdomen is enclosed by a soft skin. Among the case or caddis-worms also (Phycis, Phn/gaiiea}, which, as larvae, dwell in a case made by themselves of sand and bits of stick, and wherein also they transform themselves into pupa, a similar construction is percep- tible (pi. III. f. 1). 56. The LEGS (pcdes) of larvae take a different form, according to their position 38 PARTIAL QRISMOLOGY. The true LEGS, THORACIC LEGS (pedes merely, or pedes veri, PI. II. f. 17), are affixed to the three first segments of the abdomen, and con- sist of several joints, like those of the perfect insect. Each of these joints is inclosed in its peculiar corneous cylinder ; and it is only where these joints are connected, that a flexible membrane completes their union. By means of this arrangement we are enabled distinctly to recognise the joints analogous to those of the perfect insect, so that the leg of a caterpillar may be considered, as truly as that of the butterfly, to consist of the hip (coxa), trochanter (trochanter), thigh (femur), shank (tibia), and foot (tarsus]. It is, indeed, true that these joints, particularly in caterpillars, follow so closely upon each other, from their shortness, that the whole leg has the appearance of a small conical process ; but in many other orders, for example, in the larvae of the Carabodea, the individual joints closely approach in form to those of the perfect beetle. In general, all larvae provided with legs possess the true legs, or thoracic legs ; indeed, in most of the larvse of the Coleoptera and Diclyotoptera, these alone are to be found. The VENTRAL and ANAL LEGS, or PROLEGS (propedes, pedes spurii, PI. II. f. 18), are short, thick, muscular, unarticulated processes upon the ventral and anal segments of many larvae ; they are exclusively peculiar to this second stage of existence, and entirely disappear upon its transition to the pupa state. In form, they are sometimes short cones, with an obtuse apex ; sometimes longer thin pedicles, distended at their extremity into a flat SOLE (planta) ; sometimes indistinct, very moveable knobs or tubercles, which are protruded or withdrawn at the will of the larva. In these cases, the sole is very generally either half or entirely surrounded by a double or single row of short CLAWS, or crotchets, by the aid of which the caterpillar is enabled to attach itself firmly in climbing ; the tubercles, on the contrary, are mostly unpro- vided with them ; and, indeed, many of the prolegs of the first adduced form do not possess these claws. In many, particularly those whose sole is much distended, it is clapper-shaped, that is to say, composed of an exterior and interior flap, which move in opposition to each other like a pair of tongs, and thus form a claw. Kirby and Spence have constructed a tabular division of larvse from these differences, which we shall here introduce for the purpose of giving a general view of them. I. Larvse without feet. 1. With a membranaceous head of indeterminate shape tera, PI. II. f. 1). THE LARVA. 39 2. With a corneous head of determinate shape, (many Coleo- ptera, the Rhynchopkora, many Hymenoplera, Culicina, Tipularid), PI. II. f. 3. II . Larvae with feet. 1. With legs only, and with or without an anal proleg. a. Joints short and conical (Elaterodea, Cerambycina), PI. II. f. 4. b. Joints longer (Cicindelacea, Carabodea, Hydrocan- tharides, Brachyptera, Lamellicornia , Cuccinellacea, Neuroptera), PL II. f. 6. 2. Prolegs only (Tipttlaria, and other Diptera, (Ecophora), PI. II. f. 2. 3. Both legs and prolegs (Lepidoptera, Tenthredonodea). a. Without claws (Tenthredonodea'), PI. II. f. 5 and '/ b. With claws (Lepidoptera}, PI. II. f. 9 and 11*. Prolegs, in some instances, occur upon all the segments of the abdomen, and even upon the thoracic segments there are found legs resembling the prolegs in form, in those cases where true thoracic legs are wanting (Rhynchophora). But in the majority of cases, the first abdominal segment, or fourth segment of the body, has no prolegs, but they are sometimes observable upon this segment ((Ecophora * Burmeister, in this table, does not exactly follow that given in the Introduction to Entomology, vol. iii. p. 144. But why, after quoting it as that of Kirby and Spence, he should make alterations in it, it is difficult to say, particularly as these alterations are not material. But he refers to the German translation of their work ; and, from not knowing that book, I am unable to determine how far it was the cause of the difference : but, to do justice to these authors, I give the table in their own words : I. Larvae without legs. i. With a corneous head of determinate shape (coleopterous and hymenopterous Apods Culicidce, some Tipnlarics, &c. amongst the Diptera). ii. With a membranaceous head of indeterminate shape (Muscidce, Syrphida, and other Diptera). II. Larvae with legs. i. With legs only, and with or without an anal proleg (Neuroptera, and many Coleoptera). \. Joints short and conical (Elater, Cerambycidce, Sic.). 2. Joints long and subfiliform (Staphylinus, Coccinella, Cicindela, &c.). ii. Prolegs only (many Tipularite, and some subcutaneous lepidopterous larvae, &c.). iii. Both legs and prolegs (Lepidoptera, Serrifera, and some Coleoptera). 1. Without claws (Serrifera, &c.). 2. With claws (Lepidoptera, &c.). TR. 40 PARTIAL ORISMOLOGY. Rajella*J, and in the rat=tailed maggot (the larva of Eristalis tenax), which has no thoracic legs, but only prolegs upon the segments of its body. The following table presents an arrangement of larvae, grouped according to the position of their prolegs. 1. Prolegs upon all the segments of the abdomen except the first (eight pairs). The genus Cimbex, PL II. fj. 2. Prolegs upon all the ventral segments, excepting the first and penultimate (seven pairs). The genus Tenthredo. 3. Prolegs are wanting upon the first, antepenultimate, and penul- timate segments (six pairs). The genus Hylotoma, PL II. f. 5. 4. Prolegs upon the anal and four ventral segments, viz. the sixth, seventh, eighth, and ninth, PL II. f.9. The majority of caterpillars, namely all the hawk moths (Sphing- odea), butterflies (Papilionacea), bombyces (Bombycodea), as well as the majority of owlets (Noctuacea). 5. Prolegs upon the anal, and three ventral segments, viz. a. The sixth, seventh, and eighth. The caterpillars of many owlets. b. Upon the seventh, eighth, and ninth. Many caterpillars of the Pyralodea, Hypenarostralis. 6. Prolegs upon the anal and two ventral segments (Larvae geometrifurm.es), PL II. f. 10. The genera Plusia, Ophuisa, Acontia, Metrocampus, Lat. ; Ellopia, Tr. 7- Prolegs upon the anal, and one ventral segment (the last but three), Larva geometrce, PL II. f. 11. The majority of the Phalcenodea. 8. Prolegs upon the anal segment only. Some moths (Tineodea}, the genus Lyda, and many coleopterous larvae. 9. No prolegs upon the anal segment, but upon four of the ventral segments (the seventh to the ninth), PL II. f. 12f. The larvaa of many moths (for ex. Harpy a, Platypteryx). Naturfoi-sch. St. IV. p. 37, &r. \- This is a similar arrangement to that of Reaumur, in his second Memoir in the first volume, nol v somewhat modified and enlarged. TR. THE LARVA. 41 Besides these, the larvae of several Diptera have been described by different writers, as having, some, prolegs upon all their segments, and others only upon their first and last. Much irregularity appears to prevail in this Order with respect to the feet of the larvae, which is clearly evinced from the descriptions of those of the different families of the Order. The preceding sketch of their distribution must, consequently, suffice for the present, until we proceed to their detailed description. A precise, and, at the same time, natural division of them, is scarcely possible, from their multitudinous differ- ences; but what we have remarked above, we hope will serve, in some measure, as a guide. 57- We now proceed to the consideration of what still remains to be observed upon the construction of the body of the larvae. It has already been remarked, that it properly consists of twelve segments, which are separated from each other by slight constrictions. Beyond this, there are but few generalities to notice in it. For the most part, each of the segments, with the exception of the second, third, and last, has, on each side, a small longitudinal aperture, which is surrounded by a broad callous margin, and is called SPIRACLE, or STIGMA (spiraciila, stigma}, and by means of it the air is accessible to the respiratory organs distributed throughout the body. Many of the larvae which live in water, have, instead of spiracles, membranous laminae, or plates, throughout which the trachete, or AIR TUBES, are distributed, and which thus supply the function of gills, and may, therefore, be very properly called gill plates (branchiae, aer'iductus, of Kirby and Spence). They are distinctly observable in the larvae of many May-flies (Ephemera Phryganea). A similar respiratory apparatus is observable in the larvae of many Diptera, although seated at a different part. Some bear, like the larva of Slrntiomys and gnats (Culex), a coronet of a plumose form at their anus, by means of which they more easily sustain themselves at the surface of the water. In the middle of this coronet, or close to very similar appendages, are found the orifices of the tracheae (compare the larva of Dy(iscux); in others (Erisialifi, PI. II. f.8) a pair of thin tracheae run parallely the whole length of the body, and their orifice remains at the surface of the water, while the larvae themselves repose at the bottom of the puddles and pools. 42 PARTIAL OR1SMOLOGY. 58. Different from these peculiar appendages, which we may consistently consider as particular organs, is the spinose and hairy clothing of the majority of caterpillars. We may, indeed, admit that the majority of larva? are quite naked ; but this assertion does not admit of extension to the order of the Lepidoptera, for very many caterpillars move about enveloped in fur. The SPJNOSE cater- pillars (larvae acnleatce), are almost peculiar to the butterflies (Papi- lionacea}, but the larvae also of the tortoise beetles (Cassida), are armed nearly all over with longer or shorter spines, but particularly so upon the abdomen. In some we observe, upon each segment, four, five, six, seven, or eight simple, and indeed, not unfrequently, branched spines (Vanessa polych/oros), which gives the creature a wild and forbidding appearance, and which may contribute much to the fear with which the common man in general views these innocent and harmless caterpillars. Much more terror is frequently evinced at the indeed larger, but quite naked caterpillars, of the hawk moths, which are furnished, upon their last segment, with a straight or bent horn (Sphingodea, larvae cornutcK), of which it is fabled that it supplies the place of a poisonous and severely wounding sting. A few have, instead of this, a furcate process (Harpya, Ochs, Centra'), the branches of which are pierced, so that the caterpillar possesses the faculty of protruding slender threads through these tubes, for the purpose, as is supposed, of scaring inimical ichneumons (Larvae furciferai). But, with respect to their powers of injury, greater attention is claimed by the HIRSUTE CATERPILLARS (Larvce ursin(e), which are completely clothed with long hairs and bristles, and which, from their stiffness and sharp points, will often cause an unpleasant inflammation upon a delicate skin ; for, when rudely seized, the handling will cause it to lose its dense hair, which, by piercing the skin, causes an itching sensation, that induces the wounded person to rub the spot, and thereby produces a swelling. To go into greater detail upon the forms of larvae, appears unnecessary, as, in the natural history of each Order, a characteristic arrangement of their larvae will be at the same time given, and to which we therefore refer. THE PUI'A. 43 III. THE PUPA STATE. 59. We have now arrived at the third and last stage of development, viz., the PUPA STATE. The pupae of insects, with an incomplete metamorphosis, perfectly agree with their larvae in form and structure ; but those whose imago is provided with wings, have, at this period of their existence, the rudiments of these organs, as an evident mark of distinction. They may, accordingly, be distributed into two divisions 1. Pupa? without alary appendages, which, according to the Fabrician definition of the metamorphoses, must be called COMPLETE FUPJE, but which, according to us, are necessarily incomplete pupae. To these belong the lice (Pediculus"), the bed bugs (Cimex lectitlarius), many species of the genus Phasma *, and some other wingless Hemiptera and Ortkoptera. 2. Pupae with the rudiments of wings, according to the former definition, Semi -complete Piipce, but by us they are called Sub- incomplete. These comprise all the pupee of the winged genera of the Orders, Hemiptera, Dictyoto/ilera, and Orlhop'era. Lamarck calls nymphce all pupae with an incomplete metamorphosis. 60. In insects with a complete metamorphosis, the pupa state is a very peculiar and characteristic period of their existence. Exteriorly a perfect stand-still appears in the process of development, for the pupa, in the majority of cases, is quiescent, and does not take the least nourishment to itself; but, internally, the greater changes are in progress. In a subsequent division of this work, we shall treat in detail of these changes, for we must restrict ourselves here to the con- O ' sideration of the exterior form alone of these pupae. We divide them > into the two following groups. * Or rather of the family Phasmidce. They are all contained in the sub-family Apterophasmina, which comprises! twelve genera in Mr. G. R. Gray's valuable " Synopsis of the Species of Insects belonging to the family of Phasmidee," just published by Longman and Co., and to which we call the attention of Entomologists, as containing .an elaborate distribution of all the known species of this singular and interesting tribe. Ta. 44 PARTIAL ORISMOLOGY. I. Pupae which freely lie, hang, or are in any way fastened or attached in their particular element, NAKED PUP.E (Pupce mida}. This mode of change is not particular to any individual Order, but it occurs, as well as the following, throughout all the Orders. II. Pupae which repose in cases artificially prepared by the larvae ; INCASED PUP-ffi: (Pupce foHiculatce} , which case is called COCOON (incunabidum, folliculus) . But these differences do not at all apply to the shape of the pupa itself. The following are the terms thence given by former writers. COARCTATE and OBTECTED pupae (Pupce oblecfte, coarctatce}, are those which are inclosed in a firm, egg-shaped, corneus case, and which do not in the least indicate the parts of the perfect insect (PI. II. f. 21 ). This transformation is peculiar to many families of flies (Syrpkodea, (Estracea, Muscaria). The surrounding case is the dried skin of the larva, and, strictly considered, it is analogous to the cases of many insects with a pupa folUcidata for the true pupa, with its clearly distinguishable limbs, lies inclosed beneath this case. This kind of pupa is probably peculiar to all such insects whose larvae do not moult. MASKED PUP^; (pupce.lartiaife'), are those whose general inclosure is likewise a horny case, but upon which the different parts of the future insect are traced in lines (PI. II. f. 19). Lamarck calls both these kinds of pupae chrysalis, the former chry dolioloides, the latter chry. signata (Lepidoptera, many Diptera). EXARATE or sculptured pupse (pupee exarattf}, are such in which the limbs of the perfect insect are observed to lie free, although still closely attached to the body fPl.II. f. 24). These Lamarck calls mumia, and particularly mumia coarctala (Coleoptern, Hymenopiera), whilst the pupa? of the Phryganea, which, in the last stage of their pupa existence possess some degree of motion, he calls mumia; pseudo- nymph(e. A naked pupa is called SUBTERRANEOUS (pupa subterranea*), when, during this period of its -life, it lies buried in damp earth. But if it hangs perpendicularly with its head downwards, as in many butterflies (Hipparchia Egeria), PI. II f. 20, it is called an ADHERENT pupa (/jw/jfl adhcerens), but if placed upright against a vertical object, and supported by a delicate filament passed transversely across its thorax (PI. II. f. 26), it is called a BOUND pupa. This kind is also only found 'among the butterflies (Pontia Cratcegi). An incased pupa, whose cocoon remains partially open (Sdturn'xi, Pkryganea),is usually called a GUARDED pup;i ' iipn custodiata}. THE PUPA. 45 61. With respect to the construction of the body of the pupa, we find much more distinctly in it, than in that of the larva, the indication of the division of the body into three chief parts, the head, thorax and abdomen. This division of the body is shown by a constriction in the pupa case, as we observed, also, to be in the larva. If we, with Kirby and Spence, perhaps not quite appropriately, call this exterior sheath the CASE (thecct) of the pupa, we may then divide it into the following parts, from its now more distinctly apparent exterior organs. HEAD-CASE (cephalotheca) is the anterior hemispherical division, which incloses the head of the future perfect insect. In it we must again distinguish the EYE-CASE (optlialtnotheca), the MOUTH-CASE (stoma- totliecci), which, in the Coleoptera, incloses the mandibles and palpi ; or, as in many Lepidoptera, covers the protruding proboscis ; and, in this latter case, is called by Kirby and Spence TONGUE-CASE (glosso- theca). In front of the mouth-case lie the LEG-CASES (podotheca), inclined towards each other at acute angles ; very near to them, but directed outwards towards the back, the either long, pointed, or shorter thicker ANTENNAE CASES (Ceratofhec&y*. Next to the head-case follows the TRUNK-CASE (thorcicotlieca, cytoiheca of Kirby and Spence), which is covered below by the WING-CASES (pterothecte'), which originating at its sides, embrace it in the direction of the abdomen. The form of the trunk-case is influenced by the different conformations of the thorax in the several orders, so that the three segments of the thorax are sometimes more distinctly discriminated; and, when so we may apply the terms PROTHORACIC-CASE (prothoracotheca)* MESOTHORACIC-CASE (mesothoracotheca) , and METATHORACIC-CASE (metathoracotheca), (Coleoptera and Hymenoptera) ; but sometimes, from the preponderating size of the middle portion, we observe all the three divisions unite in one (Diptera, Lepidoptera). Immedi- ately upon the trunk-case follows the ABDOMEM-CASE (gasterothecd), which consists of nine (more or less) distinctly separated segments; and at its apex we observe the future anal orifice indicated ; and on both sides of each segment the easily recognisable SPIRACLES (stigmce, spiraculce) are perceptible. The apex of the last segment (apex abdominis, cremaster of Kirby and Spence) it is still important to notice, from its truly innumerable differences. Very generally it terminates in a conical, either acute or * Not CeraiheccB, according to Kirby and Spence. 46 PARTIAL ORISMOLOGY. obtuse process (Sph. ligustri), or there are two close together (Noct. amethystina), which sometimes, as in Hydroph-piceus. Noct. lucipara, hang downwards as long bent hooks. Sometimes we observe many little crotchets or points ; and, also, as in Harpy a Fagi, an indented pectinated process (P. II. f. 25, and other forms in f. 22 and 23). If the abdomen terminate in a protruding ovipositor (Sirex, Pimpla, Cryptus), this, also, has its peculiar case (acidotheca) ; which, when the ovipositor is short, stands forth free (Sirex); but when much longer, as in Pimpla, it is turned round upon the venter, or the back of the pupa. 02. The superficies of pupae is still more generally naked than that of larvae. But few instances have been hitherto observed, in which they are covered with isolated bristles (Hydroph. piceits), or fasciculate (several Bombyces, for example, Orgyia pudibunda, Pygera buce- phala*), or covered with wreaths of hair. The processes, and angular or produced parts of the pupa itself, which arise from the form of the included insect, must be clearly distinguished from such clothing. With these processes may be classed the already described apical spines, and the also before indicated protruding proboscis of many Lepidoptera (glossotheca). In the hawk moths (Sphinx Convolvuli, Ligustri), it presents itself in an obtuse club, bent towards the body between the two first pair of legs; in the owlets (Cucullia Tanaceti, Plusia con- sona, and others of these genera), it protrudes as a clavate process beyond the legs, and then lies free opposite the first ventral segments of the abdomen. The tracheae, also,, of many dipterous pupae which live in water, for example, of the gnats (Cule#), in which they project from the sides of the thorax as two clavate processes, well deserve to be mentioned here. Shorter processes, such as spines and wrinkles, arise from several portions of the body of the pupa, and exclusively belong to its case. Thus the pupa of the stag-beetle (Lucanus cervus) has, upon the sides of its first abdominal segment, several spines united in a bundle, resembling those of the Hydroph. piceus, in front of its thorax, or the pupa of an Asilus, figured by De Geer, with spines upon its head, and abdominal segments f . The pupa of the goat moth ( Cossus ligniperda) * Burrueister has evidently made a mistake here ; for the pupa of Pygera bucephala is perfectly smooth The pupa of Leucom'a Salicis would have been a better example. TR. t Memoirs, 76, pi. 14, fig. 8. THE PUPA. 47 has, upon the sides of each abdominal segment, a row of slight crotchets, as have, also, many other lepidopterous pupa? ; in many they present themselves as elevated, somewhat notched, or indented stripes (admi- nicula of Kirby and $ pence). 63. Many pupae have other protuberances, which, from their shortness and thickness, can neither be considered as processes nor as spines, but are merely prominent angles, which equally proceed from the form of the inclosed insect, and are exclusively peculiar to the pupae of some Lepi- doptera, and Diptera. These forms are found only among the butter- flies of the former order ; of which they are, however, the characteristics of the majority. In general, two conical processes rise in front of the eyes ; these appear to enclose the palpi of the butterfly, and are then called PALPI-CASES (pselaphothecce) ; then the trunk-case expands in several lateral angles ; but chief of all is the process upon the back, in the form of a long pyramid, or resembling a man's nose, so much so, that a pupa of this description, upon the first glimpse of it, looks like a human face, particularly when, as is often the case, there are dark spots within the impressions above the pyramid, which, consequently, have all the appearance of eyes. Pupae, thus formed, are called ANGULAR (p. angularex); the rest, in contradistinction, are styled CONICAL (/>. conicce). 64. Before we conclude our consideration of the pupae, we will add a few words upon their different colours. All pupa? which are placed in shady, dark situations ; for example, in the earth, or in water, or in perfectly obscure dwellings (as the obtected pupae) are of a yellowish white, but which become darker upon exposure to the light ; the rest, particularly the pupae of the nocturnal and crepuscular Lepidoptera, and of the minute moths, &c. are of a bright brown when their place of concealment is within the earth, but they are darker when they are inclosed in transparent webs. The majority of the pupae of the diurnal Lepidoptera have a greenish, or yellowish grey brown colour, many are speckled (Pontia Cratoegi), others have large spots of a glittering gold colour upon the thorax and abdomen, and they alone thence obtain the name of chrysalis, aurelia, which names have been applied in general, but chiefly by early writers, to the pupae of all the butterflies. 48 PARTIAL ORISMOLOGY. / IV. THE INSECT IN ITS PERFECT STATE (Imago}. 65. An insect, when it quits its pupa case, is called PERFECT (imago, insectum dedaratum, perfectum). Upon observing it more closely, we immediately detect several divisions of the body, which have become now more distinctly separated than they were in the earlier stages of its existence. Henceforward we always observe three chief divisions, which are called HEAD (caput), THORAX (thorax), and ABDOMEN (abdomen). We will now take these parts consecutively, but prievously insert an observation or two upon the name of these creatures. It is from this division of the insect body that the various names which have been applied by naturalists for the designation of the class, are deduced. Aristotle, the most ancient of all, called insects "Evrofj.a, which word is derived from ivre^veiv, to cut in. His name, therefore, very evidently refers to the divided body of these creatures. The Roman writers followed the example of this great man, and called our favourites Insecta, derived from insecare, which likewise signifies, to cut in. This name was adopted by all authors, and Linne introduced it among the systematic names of animals, whence'it has passed into almost all the living languages. The Germans have also long used the word, insect ; but Oken, latterly, when he sketched his German nomenclature for all natural bodies, called insects Kerfe, a word which has doubtlessly the same signification, he having derived it as we surmise, we conceive correctly, from Kerben, to notch, or indent. Other German writers, as Carus, Wagler, Burmeister, &c. have adopted Oken's term, as having in fact the great merit of being of genuine German extraction, and which at the same time equally well preserves the advantage of a designation expressive of the predominant character of the class.* * We retain this latter paragraph, which has rather a German than an English interest, in deference to the opinion of a very distinguished man. But it may be of use, from the German language having now become so prevalent and important a study, to explain a term which has not yet found its way into the dictionaries, and which, possibly, every writer may not think it necessary to illustrate when employing it. TR. TIIK HEAD. 49 I. THE HEAD (Capvt). 66. The HEAD *, the first of the three divisions of the insect body, displays considerable variety in its form. In general it approaches to the globose, or semi-globose, and is surrounded by a plain corneous case, and contains the different organs of the senses. From its sim- plicity, it is evident that we cannot so readily distinguish by peculiar terms particular divisions in it, as we can certain regions, and these must agree with the analagous portions of the head of the higher animals. With respect to the most usual forms of the head, modifications of the globose seem to prevail, with the occasional predominance of either its longitudinal or transverse diameter. Thence proceed the egg-shaped, longitudinal, obtuse-triangular, heart-shaped forms, &c., which we meet with in so many groups of insects. It is very fre- quently produced into notches and prominences which are called HORNS (cornua) ; these are always integral portions of the corneous case, and are never articulated and moveable. 67- The following are the portions of the head most usual to note. We must first distinguish the true SKULL (cranium, calva according to others), and thence proceed to the generally moveable organs attached to it ; it therefore comprises the whole of the head, excluding the antennae, eyes, and oral apparatus. If we wish to notice the upper part, from the front across the vertex to the posterior cavity, we call it UPPER-HEAD, SKULL-CAP (calva, epicranium, Straust), PL HI- f. 11, A. It is limited in front by the CLYPEUS (ch/peus), called LOWER FACE (Jiypostoma, in the Diptera by Meigen and Bouche, the epistomis of Latreille), or that portion which lies above the organs of the mouth ; it is bordered laterally by the sides of the head, and extends as far as * 111 explanation of our occasionally differing from other writers in the nomenclature of the parts of the insect body, we refer to what we have said at 9, II. and the note. j- Considerations Generales sur rAnatornie comparee des Animaux articules. Par Here. Straus-Diirckheim. Paris, 1828. 4to. av. 10 fig. (p. 52, &c). E 50 PARTIAL ORISMOLOGY. the eyes (PI. III. f. }], c). Kirby and Spence call tliis part the NOSE (nasus), and distinguish the anterior part as rhinarium, and the more lateral ones as post-nasus ; certainly without foundation, for although many naturalists have supposed the organs of smell to exist here, none have yet been able to prove they do so, and we must therefore decidedly reject a name founded upon such a supposition. The FRONT, FOREHEAD, or BROW (frons), is that portion which intervenes between the posterior margin of the clypeus between the eyes, to where the head commences to be flattened above (PI. III. f. 11, B). Nitzsch distin- guishes that portion of it which lies between the eyes as MIDDLE HEAD (sinciput). VERTEX (vertex) is the upper flattened portion of the head upon which very generally the simple eyes or OCELLI (ocelli) are found (PI. III. f. 11, a). In many insects, particularly Coleoptera, the vertex is not apparent, as they bear their head withdrawn into the thorax. FACE (fades) is the anterior portion of the head above the mouth, and includes the clypeus, the front, and the parts bordering upon the eyes. It is chiefly from the front and the vertex that the above-mentioned prominences originate, called HORNS (cornua), from their frequently not inapt resemblance to the horns of the ruminants. These parts are often covered with hair, which is then called HEAD HAIR (capilli) a fringe of hair seated upon the clypeus, over the mouth, is called WHISKER (mystaai), and is found chiefly among the Diptera in the families of the flies of prey (Asilica) and the true flies (Muscaria). The lower part of the head is divided into the following portions. The GULA (gula, PI. III. f. 12, D), or THROAT (jugulum) extends, according to Kirby and Spence, from the anterior portion, where the chin (see below, 68) is attached, or from the orifice of the mouth in general to the commencement of the neck, and comprises consequently the whole middle portion of the lower head, and which Straus calls, from its being the support of the whole, the basal part (basilaire, pars basalis). In many of the Coleoptera, for example in Geotrupes nasi- cornis, it is produced into a smooth boss ; in other instances (Carabus], this part is sloped, and its anterior raised margin, to which the chin is attached, is swollen into a thick callosity (PI. III. f. 12 and 13, d.). When it assumes this form, some entomologists are inclined to call it, but very injudiciously (consult 9, ii. and note) head-breast-bone (sternum capitate). Straus correctly considers this swelling as belonging to the basal part, and which he calls prebasal part (pre- basilaire). THE HEAD. 51 The sides of the head, from the eyes downwards to the mouth, are called CHEEKS (gencp, PI. III. f. 14, E), particularly when they consi- siderably protrude, as in some of the Diptera (Myopa\ We again distinguish in them the anterior portion, extending as far as the articulation of the mandibles and maxillae., or the commencement of the mouth, by the name of reins or LORA (lora, PI. III. f. 13, E), and the posterior portion lying proximate to the eyes, as the TEMPLES (tempora, PI. III. f. 13, F). The back of the head around the commencement of the neck is the OCCIPUT (occiput, PL III. f. 12 14, G). In many instances, chiefly among the Coleoptera and Ortlioptera, in which the longitudinally formed head is deeply withdrawn within the thorax, this portion is not at all visible, but it is prominently perceptible in the Diptera and Hymenoptera, which carry their heads free. The aperture behind the head, through which the internal organs are continued, is called the OCCIPITAL FORAMEN (foramen occipitale). In many insects the commencement of the nock is likewise an inte- gral portion of the head. The NECK (collum) is that part which unites the head with the thorax. In the majority it is merely a membranous tube, and it is among a few of \\ieColeoptera only (Staphylinus, Leptura} that the back of the head is constructed into a short corneous cylinder, to which the membrane of the neck is attached. Some entomologists call this part the COLLAR (collare), a name which is applied by others (for example, Klug, Kirby and Spence,) to the prothorax of the Hymenoptera. THE MOUTH (Os). 68. From this consideration of the different parts of the head we pass on to the investigation of the several organs attached to it. These are the PARTS OP THE MOUTH, the ANTENNA, and the EYES. The ORAL ORGANS, or parts of the mouth (partes oris, instrumenta cibaria, trophi) lie at the anterior, or inferior part of the head, and surround the MOUTH (os). When attached to a long corneous and generally cylindrical prolongation of the head, this part is called the snout or ROSTRUM (rostrum), which, however, must be well distin- guished from the proboscidal prolongation of the oral organs them- selves ; the rostrum being merely a continuation of the corneous cover- ing of the head, and not a distinct organ. E 2 52 PARTIAL ORISMOLOGY. The exact description and knowledge of the oral organs is of great importance in Systematic Entomology, as these parts supply the charac- ters of many genera, and not rarely of entire families: we must, con- sequently, here give a very precise definition of their forms. In the first place we must distinguish the BITING organs (instr. cib. mordent ia, s. libera) from the SUCKING ones (instr. cib. suctorict) ; and the former are also specially called MASTICATING organs (instr. masticandi) ; these stand freely beside each other, and display much uniformity in their structure as well as great regularity of shape *, whereby they announce a superior degree of development, so much so, that insects with a masticating mouth, notwithstanding its very similar conformation, take the precedence of those with suctorial organs. The latter are more or less united together, and assume very different shapes in the several orders, of which we shall particularly treat below- The masticating mouth (as found in the Coleoptera, Dictyotoptera, Neuroptera, and many Hymenopterci) consists of the following organs : The upper lip, LABRUM, (labrum, labium superius, PI. III. f. 11. i), is very generally of the form of a segment of the circle, or a triangular, or quadrangular, somewhat convex corneous plate, which is united posteriorly by a membranous hinge with the clypeus. Fabricius f originally called this organ clypeus, in which he was followed by Illi- ger {. This latter writer applied the name of labrum to the narrow anterior appendage of the true labrum, which is very seldom present, but is found in some of the Hymenoptera (Hylceus), and is called by Kirby and Spence the APFENDICLE (appendicula}. The upper jaws or MANDIBLES (mandibulce, PI. III. f. 11 13. o, o), which are two strong, corneous, somewhat bent hooks, their inner margin being more or less dentate ; and which articulate with the cheeks at their broad basis, and move by ginglymus, opposed to each other like the blades of scissors. The under jaws or MAXILLA (maxillae, PI. III. f. 12 and 13, P, P), are also a pair of organs which in many respects resemble the mandibles, although smaller and more delicately constructed. They are not simple, but distinctly consist of four pieces. The two first hang attached to * See what Kirby and Spence say upon their variety, Introduction to Entomology, vol. iii. p. 473 ; what Burmeister says above must be taken comparatively TR. j- Philosoph. Entom., p. 37. + Terminologie, p. 220. Burmeister says it is the genus Hylaus, without indicating that he means of Fabricius. I know it only in the females of the genus Halictus, which are comprised in the above genus of Fabricius TR. THE HEAD. 53 each other as well as to the head and labium by means of soft liga- ments ; the lowest, the HINGE, (cardo, PI. III. f. 16 and 17, 1> 1, or the BASE, pars basalts; according to Straus, branche transversale,) is narrow, thin and transverse, and articulates with the throat, forming a right angle with the one that follows it, which is the STALK (stipes, piece dorsals of Straus, 2, 2 of the same figure), and is thicker, stronger, and larger, and above somewhat horny, but beneath softer and mem- branaceous. Closely attached to this is the third piece, which is a corneous scale, at the anterior margin of which the palpus is inserted (thence called squame palpiftre, by Straus), and which forms beneath the case or covering of the maxilla. The fourth piece (the same plate and figure, 4, 4) borders upon the two preceding, and is completely horny, hooked, its interior margin concave, or, as well as the stalk, covered with short stiff bristles. It is called the MAXILLARY LOBE (lolus maxillae, intermaxillaire of Straus), from its more generally taking the appearance of a superior appendage of the stalk. In many insects, particularly the Hymenoptera and coprophagous Petalocera among the beetles (for example, Copris, Aphodius), it is a simple, variously formed, flat, coriaceous scale, with its margin beset with short hair; in others, as among the Capricorn beetles (Lamia, Cerambyx), it is thicker, and more solid and compact, and is divided into a harder, INTERNAL (lobus internus}, and more membranaceous, EXTERNAL LOBE (lobus extemus). This exterior lobe is the same organ which in the Orthoptera covers the internal lobe like a cap, and then takes the name of HELMET (galea, PI. III. f. 17, 5 of Cychrus, PI. IV. f. 2, 5 of Copris}. In many insects it is wanting ; in other instances it occurs as a two-jointed filiform appendage, and this is then the second internal maxillary palpus, as already Illiger * very correctly indicated. It is exactly where the lobes border upon the stalk that the maxillary palpi are also inserted. The underlip, or LABIUM (plainly labium, or labium inferius), which is that organ that assists to close the orifice of the mouth from below O (PI. III. f. 12 and 13, Q). It consists of two chief parts, each of which may be considered as a separate organ ; these are, The CHIN (mentum, PI. IV. f. 3 and 4, A, A), a thin, sometimes trian- gular, sometimes of the shape of a segment of a circle, or trapezoidal corneous plate, deeply emarginated upon its anterior side, and con- nected, like the upper lip, to the clypeus, by means of a membrane, * Sec Kaefer Preusscns, 1 Vorrcdc, p. xxxvi. note 15. 54 PARTIAL ORISMOLOGY. with the margin of the throat (the sternum capitale of some entomolo- gists), and forms from beneath the inferior covering of the mouth. The TONGUE (ligula, Fab.; lingua, Kirby and Spence, PI. IV. f. 4. B) reposes internally upon the chin. It is, in general, a membranaceous or more or less fleshy organ, which frequently protrudes beyond the anterior margin of the chin, in which case its exterior inferior side is horny; this horny part is then called TONGUE-BONE (os hyoideum), or FULCRUM (fulcrum). The LABIAL PALPI (palpi labiates^) are close to this, and indeed frequently inserted upon it. The upper fleshy part, the true tongue, is frequently simple, and visibly separated from the chin (PL IV. f. 5), as in the Orthoptera and Xenroptera; in other cases it is divided, and very closely connected with that organ (Coleoptera). In the wasps it is separated into several (three or four) lobes. In the bees it projects as a long cylindrical, frequently pubescent, retractile filament : in some of the fossores (Scolia} this filament is divided into three. Illiger and Latreille call the tongues of insects with a masticating mouth the labium ; in Fabricius, on the contrary, the labium is some- times our mentum, and sometimes, when the chin and tongue are not distinctly separated, the whole inferior flap of the mouth. The already frequently mentioned FEELERS (palpi) are the auxiliary organs of a masticating mouth ; they are many -jointed and but seldom simple appendages, inserted upon the maxillae and labium. Those upon the maxillae, the MAXILLARY FEELERS (palpi muxillares, PI. III. f. 16, A), generally originate from where the scale is connected with the external lobe, and are united to it by a very supple hinge. The LABIAL FEELERS (palpi labiales, PI. IV. f. 3. c, c) are placed late- rally upon the labium, close to the tongue, more or less approximate to the part where it projects beyond the chin (Cerambycina, Carabodea) ; in other instances tbey are decidedly inserted in the margin of the chin (Libellula, Lamellicornia}. The number of the joints of these organs, whose length, form, and relation to each other, is very various, never exceeds six ; and, in general, the labial palpi have fewer joints than the maxillary. We have already spoken of a third two-jointed pair of feelers the INTERNAL .MAXILLARY PALPI (palpi maxillares interni, PI. III. f. 17, 5, and PI. IV. f. 10, 5), which are found only in the tiger beetles (Cicindelacea), the Carabodea, and the water beetles, and which are analogous to the HELMET (zalca) of the Orthoptera^ THE HEAD. 55 69. Before we pass on to our general consideration of the organs [of the suctorial mouth, we must give the most remarkable differences of the above-named masticating organs; but we will first notice the relations of the head to the thorax, as well as the proportions of its own parts. We observe in the head the direction in which its longitudinal diameter stands to the axis of the body. If they form one plane, it is called PROMINENT (promincns, Elater) ; PORRECT when it pro- jects, likewise horizontally, far from the thorax (Agra) ; NUTANT (nutans*) when its longitudinal diameter forms an obtuse angle with the axis of the body (Feronia, Amara, Harpalus ; PERPENDICULAR (perpendicukire) is when its longitudinal diameter forms a right angle with the axis of the body (Saperda, Diptera, Hymenoptera'}. We must next observe the manner of its connection with the thorax. FREE (exsertum or liberuni) is a distinctly visible head, never covered by the thorax (Agra, Anthia, Hymenoptera , Diptera). INSERTED (insertum), when it is partly, particularly the occiput, concealed within the thorax. RETRACTED (retractuin), when it is concealed as far as the brow within the thorax (Bupreslis). CONCEALED (abscondituni), when it is entirely withdrawn within the thorax, or is covered above by the thoracic plate (Cassida). RETRACTILE (retractile) when a thus concealed head can be pushed forwards at the will of the insect (Hi&ter). VERSATILE (versatile), when it can be freely moved every way (Hymenoptera, Diptera). From its anterior margin it is distinguished into CLYPEATE HEAD (c. clypeatum, PI. IV. f. 6), when tolerably flat, and the margin of the clypeus and the front are produced into a broad border ( Copris, Ontho- pliagus, Ateuchus} ; TURRETED (c. turritum, PI. IV. f. 7)> when it is produced anteriorly and above into a pyramidal point (Truxafcs). We have already mentioned HORNED (c. cornulum) and ROSTRATE (c. rostraium) heads. A head furnished with swollen cheeks is called BUCCATE (c. buccatum, PL IV. f. 1, Myopa). With respect to the differences of the masticating organs themselves, we shall proceed as we did in their description, by taking them consecutively. The upper lip, or labrum, differs as to its figure, surface, margin, 56 PARTIAL ORISMOLOGY. and relation to the other organs of the mouth ; there are, however, no differences exclusively peculiar to it, and we may consequently refer to General Orismology for the notification of its discrepancies, without the necessity of repeating them here. In explaining the construction of the upper jaws (mandibulce, PL IV. f. 8), Kirby and Spence have, and we think very happily, instituted a comparison with those of the superior animals. They consequently distinguish the PROSTHECA (prostheca] in the mandibles, which is a cartilaginous process, near the base within, and is found very generally among the Brachyptera ; for example, in Staphylinus incucillosus. They call TEETH {denies) the pointed processes on the inner side, and very skilfully distinguish the superior, compressed, sharp edge as CUTTING TEETH (denies incisivi, the same figure, a) ; or they call them CANINE TEETH (denies laniarii, s. can in i), when they are very- sharp and conical. GRINDING TEETH (denies molares') are the inferior thicker teeth, provided with a broad grinding surface (Melolonthd). The MOLA, or grinding surface (mola, the same tig. b), they call the broad, flat, and often, like the teeth of the elephant, ridged space of the molares of many insects (for example, of the Bombi, Melolontha, &c.). In the Coleoptera, this molar tooth is clothed laterally with short stiff hair, which Straus calls the BRUSH (brosse). The processes at the base are also important, from their supplying the articulation of the mandible with the head ; they are three in number, and are placed at the ends of the edges, beneath which the three surfaces of the mandibles join. The lower one, viewing the mandible in its natural position, is shaped like a ball, and corresponds with a cavity, or socket, in the head. The upper one, on the contrary, is concave, and consequently forms a socket corresponding with the ball upon the head-case (the same fig. d). The third is less observable, and lies within towards the orifice of the mouth, at the end of the masticating edge of the mandible (the same fig. e). The muse, adductor mandibulce is attached to it ; its antagonist, the muse, abductor, is inserted in the exterior margin, between the two articulating processes. The upper jaws very gene- rally consist of a firm corneous substance (mandib. corneas) ; in other instances they are membranaceous (m. membranacete), as in the Lamelli- cornia coprophaga: in these also they have in general a hooked shape. In the Hemiptera, and many Dlptera, they are SETACEOUS (m. setacece, xetce rostri) ; but in other families of the latter order (Tabanica) they are LANCEOLATE (m. lanceolatce). Very similar forms are observable in the under jaws (maxillae}. The THE HEAD. 57 teeth upon the inner margin of the maxillse, when present, are more uniform, finer, and more delicate ; they are frequently, however, wholly deficient,, and in lieu of them there are short bristles. In other instances the whole superior process of the under jaw is clothed with short hair, and such maxillae are called PENICILLATE (max. penicillatee, PI. IV. f. 9) ; for example, in Lucanus. But this superior lobe presents itself much more generally as a pergameneous, variously-shaped plate (max. membranacece, PL IV. f. 2). They are SETOSE (max. setosce, s. setce rostri infer lores) in the Hemiptera and many Diptera ; in some of the latter (Tabanica) also LANCEOLATE (max. lanceolate?}. They are UNGUICULATE (TO. tinguiculatfe), when the terminal tooth is moveable, and can be moved to, and withdrawn from, the internal margin of the superior lobe at the will of the insect (PL IV. f. 10). This superior development of the lower jaw has hitherto been detected only in the tiger beetles (Clcindelacea). We shall find the differences of the labium much more various than any of the yet examined organs., probably by reason of its being more compact than either of the others. We will first observe the chin, upon which we may almost repeat what we said above of the labrum ; the differences of form are also found in many other organs, and thus, as GENERAL, have been already described in the first chapter. One peculiarity is its being more or less deeply divided into two or three lobes, as well as its globose convexity in the dragon-flies (Libellulhia, PL IV. f. 11 ). The tongue also has but few exclusive peculiarities, and these we have already mentioned ; con- sequently nothing further remains to be said upon it. The under-lip of the larvae of the dragon-flies is of a very singular nature. The chin is a thin stalk, which, in its pliable articulation, can be withdrawn to the prothorax. Attached to it in front, and similarly articulated, is the flattened, nearly longitudinal, heart-shaped tongue, which, in repose, closes the orifice of the mouth, but which can also be distended as a prehensile instrument. In front of the tongue there are two claws, which, like the nippers of a pair of tongs, move in opposition to each other, and thus capture objects between them. With these the larva seizes its food, which consists of small water-insects, and then with- draws its chin and tongue, so that its prey is brought directly in front of the orifice of the mouth, when it very quietly sucks the insect dry. The claws are analogous to the labial palpi. Much more various is the construction of the palpi. With respect to the number of their joints they are subject to great variety ; but the 58 PARTIAL ORISMOLOGY. maxillary palpi have never more than six, and the labial palpi but seldom so many as FOUR joints. In every order a certain relation between their numbers appears to be followed, to which, however, there are a few exceptions. In the Colecptera, for example, the maxillary palpi have very generally four joints the labial palpi three j in the Orthop- tera, the former five the latter three ; in the Hymenopteret, the former six the latter four, but with very many exceptions, particularly in the maxillary palpi ; for example, Sirex has but one joint. Among the Neuroptera these numbers are five and three ; among the Lepidop- tera, two, or more rarely three joints in both ; the Diptera have one, two, or four joints. The Hemiptera are destitute of palpi ; but if the jointed sheath of the promuscis may be considered to represent them, we shall also here very generally find three or five joints. The most usual shape of the feelers is FILIFORM (palpi jilifurmes, PI. IV. f. 12, a) ; that is to say, such which have all their joints of an equal cylindrical shape ; MONILIFORM (p. moniliformes), when the joints are globose, like beads ; SETACEOUS (p. setace.'i), when tolerably long palpi become gradually thinner, and the last is pointed. On the con- trary, they are CONICAL (p. conici, PI. IV. f. 13, a}, when the joints are very short, and each successive one is smaller than the preceding (the Curculionodea]. The greatest differences, nevertheless, proceed from the form of the terminal joint, for the first ones are almost invariably cylindrical or ovate, and the last only differs in its form. We have thence the following designations : SECURIFORM (p. securiformes, PI. IV. f. 14), when the last joint is broadly triangular, and hangs by a point to the preceding (Securi palpata} . LUNATE (p. lunati, PI. IV. f. 15), when the same joint has the form of a half-moon (Oxyporus). FASCICULATE (p.fasciculati, PI. IV. f. 16), when it is split into many threads and processes (Lymexylon). LAMELLATE (p. lamellati, Pi. IV. f. 17), when they are divided longitudinally or transversely into several leaves (Alractocerus}. SUBULATE (p. subulati, PI. IV. f. 19), when the last joint forms with the preceding a fine and delicate termination ( Trechus). CLAVATE (p. clavati, PI. IV. f. 20), when the whole organ becomes thicker towards its apex (Trox). WEDGE-SHAPED (p. cuneif onnes}, when the last joint has the form of a wedge, which is attached by its sharp end to the preceding joint ((.'arabus, Calo oma, Cychrus, PI. III. f. 16, t). THE HEAD. 59 TURGID {p. turgidi, PI. IV. f. 22), when the last joint has the appearance of a distended bladder (G ryllotalpa). EXCAVATED ( p. excarati, PI. IV. f. 23), when the same joint is concave at its extremity. (Compare below in the Anatomy of the Organs of the Senses, 198). TRUNCATED (p. truncuti), when the last joint appears to terminate abruptly (Prionus). DIVIDED (p.fasi), when the last joint is divided longitudinally. PILOSE (p. pilosi), when the joints are covered with sharp stiff bristles (Cicindela, PI. IV. f. 10). SQUAMOSE (p. squamosi), covered with broad scales (Lepidoptera, PI. IV. f. 24 and 25). ELONGATE (p. elongati), are those palpi Avhich stand freely from the mouth (Carabus). SHORT (p. brevissimi), when, in looking at the mouth, they are not perceived (Curculionodea, Libellulina). VERY LONG (p. longissimi) , when they are longer than the head, or even than the antennas (Hydrophilus). UNEQUAL (p. intequales), when single joints take a different form (Banchus, Ichneumon, PI. IV. f. 26). EQUAL (p. cequales}, on the contrary, when this is not the case. SUCTORIAL ORGANS OF THE MOUTH. 70. The suctorial organs (instrumenta suctoria) are, fundamentally, merely the masticating ones transformed, or rather those stopped upon a lower stage of development, for a precise investigation clearly redis- covers the same identical organs. We however find no general uniformity among them, excepting in their function that of taking nourishment by suction ; for every order of insects with suctorial organs has a pecu- liar and then throughout all the families which compose it, a very uniform structure. We thence distinguish the following principal forms: the PRO- BOSCIS (proboscis), or HAUSTELLUM (Jiaustellum), we find in the Diptera only. It consists of a membranaceous or more or less fleshy organ, which descends in a perpendicular direction from the orifice of the mouth, and which in general shortly from its origin is geniculated forward, and terminates in a napper-shaped suctorial surface. Upon the 60 PARTIAL ORISMOLOGY. superficies of this membranaceous sheath, and generally at the angle of the knee,, is found the mouth, covered by a small horny flap, and sur- rounded by several bristly or lanceolate organs. Frequently, indeed, this muscular sheath consists merely of a corneous channel, in which the bristles lie (for example, Culex) ; and when thus formed, Fabricius calls it haustellum; but the muscular sheath itself, proboscis styled by Kirby and Spence the theca. The following, however, is the definition of these parts : The SHEATH (PI. V. f. 1. A), whether it be muscular or horny, represents the under lip, and is thence called labium, and the upper portion of the knee the STALK (stipes); when horny posteriorly, it is the CHIN Amentum'). The anterior terminal flap is merely a feeler, and represents the labial palpi, which also only serve to supply the place of a muscular lip ; it is called the KNOB (capitulum, PI. V. f. 1, A). Upon the stalk, close to where the bristles, or setae of the mouth are found, are placed the, from one to four-jointed, palpi (PI. V. f. 1 7- c, c). The setae themselves are concealed by the superior, broader, somewhat convex, upper lip (PI. V. f. 2 a, 3 a, and fig. 5, SHEATH, vagina, Fab., valvula, Kirby and Spence) ; beneath it lie from one to five setae, the two upper ones of which represent the MANDIBLES (the same, b. b. the KNIVES, cultelli, of Kirby and Spence) ; the two lower ones, the MAXILL/E (the same, c, c, the LANCETS, scalpella, of Kirby and Spence); the middle one, the TONGUE (the same d, here called glossarium) ; between them lies the MOUTH (the same, fig. 5, e). When there is but one seta, it is the tongue : it is also the true piercing instrument, which is pushed down into the upper channel of the under lip ; and thus embraced by the terminal flaps, pierces into the aliment ; the jaws move up and down by its side, and form, while the suctorial ventricle distends, a decided pump, in explanation of which we shall go into greater detail further on. The PROMUSCIS (rostrum, promuscis of Kirby and Spence, PI. V. f. 8) is peculiar to the Hemiptera. It is much more uniform in its construction than the proboscis, although it generally consists of the same identical parts. We must distinguish in it the small triangular plano-convex UPPER LIP, (labrum, fig. 8, 9, and 11, a, from above, fig. 14 from beneath), which incases the commencement of the pro- muscis from above, and is attached to the clypeus ; and the, from three to five-jointed, sheath (fig. 8. b), which consists of two equal lateral flaps, which may represent the maxillae and their palpi, and four fine setae (fig. 10, c, c, and d, d), which, as in the flies, are analogous to THE HEAD. 61 the upper and under jaw. Between them is found the orifice of the mouth, at the apex of a small lanceolate tongue, concealed within the sheath (fig. 10, e, and fig. 13, e}, which is enclosed by the setae of the jaws. The jointed sheath of the promuscis is called vagina; the setae of the jaws, setce super lores et inferior es ; the central tongue, ligula. The SPIRAL TONGUE (lingua spiraUs, Fab. ; antlia, Kirby and Spence: spiritrompe, Lat.), or sucker of the Lepidoptera, is the third form of a suctorial mouth. It equally consists of all the organs of a masticating apparatus, which, however, here, adopt the following configuration. A small triangular piece, attached to the clypeus, and which extends downwards towards the mouth, is the LABRUM (fig. 15, a, and fig. 16); near to it are placed the short, conical, slightly-bent MANDIBLES (fig. 15, b, l>, and fig. 17)- They are both covered by the large forward ly-bent labial palpi (PL VI. f. 3, d), and can be dis- covered only by a very laborious research. The MAXILLAE have the same form they are described to take above in the masticating appa- ratus ; but the superior lobe is stretched into a long, cylindrical, transversely-wrinkled filament (PI. VI. f. 1,); at the inner margin of which, two narrow bands are found (fig. 2, a, a), which symme- trically agree with those of the other maxilla, and by means of which, therefore, the space occurring between the two maxillae is formed into a tube (fig. 2, o). The filiform maxillae are also hollow (fig. 2, p, p), and by these cavities they are connected with the furcate commence- ment of the eesophagus, so that the Lepidoptera have, as it were, two mouths, or rather two separated suctorial tubes. Where the upper filament of the maxilla is attached to the stalk, a small two-jointed FEELER (fig. 1, b} is inserted. The LABIUM (PI. V. f.18, e, and PI. VI, f. 4, e}, is tolerably large, generally triangular, and frequently divided at its apex. Each lobe bears a large, three -jointed, very hairy FEELEK (PI. V. f. 18, d, d, PI. VI. f. 3 and 4, d, d), which falls forward, and forms the sheath of the sucker, when it is drawn up spirally in repose. The suctorial organ of the bees (PI. VI. f. 2 9, see description of the plates), and of the other suctorial Hymenoptera, is but a more or less prolonged transformation of the masticating apparatus, the same as that of the May flies (Phryganeodea), and we shall therefore treat of them in detail in our systematic description of their families. The mouth of the flea (Puhx), to which Kirby and Spence ascribe a peculiar suctorial organ, does not essentially differ from the structure of those of the Diptera, which have no fleshy lip ; and which we shall also 62 PARTIAL ORISMOLOGY. treat of in its proper place. The same observation refers likewise to the lice (Pediculf). THE EYES. 71- Having now concluded this detailed description of the oral apparatus, we can pass on to the consideration of the other organs, and the eyes occur as the most immediate objects to proceed with. The EYES plainly (oculi, PL III. f. 11, 12, 13, a. a., PI. V. f. 15, A., PI. VI, 3 and 8, A. A.) also called COMPOUND EYES (oculi composite), are placed at the sides of the head, above the mouth, and generally present themselves as large hemispheres, the superficies of which, at least upon close investigation, appear to consist of numerous regular hexagonal surfaces. They are generally circular in circumference, but many other figures (as OVAL or KIDNEY-SHAPED) are observable in them. Each of the above hexagons is itself an eye (as we shall more explicitly illustrate below in the Anatomy of the Eye), their surfaces consequently are so many slightly convex horny cases, whence the quick sight of these creatures is readily explained. Their margins of sepa- ration are often thickly set with hair (oculi pilosi), in other instances they are naked '(oculi nudi). The number of these lenses or facets has been calculated by several authors, and their almost incredible multitude has very justly excited astonishment. Hooke counted 7,000 in the eye of a house fly ; Leuwenhoek more than 12,000 in the eye of a dragon fly ; 4,000 in the eye of a domestic fly ; and Geoffroy cites a calculation, according to which there are 34,650 of such facets in the eye of a butterfly. They must also necessarily be very numerous in the eye of the Lamellicornia, in which, even under a tolerably strong lens, the divisions are not perceptible, whence Fabricius * called them simple eyes. The general rule is for the eyes to be separated by the brow (ocuh distantes), but they frequently join closely together in male insects (oculi approximati, for ex., in the dragon flies, the male Syrphi, the Drones). There are, in general, but two of these compound eyes, but a few exceptions are found to the universality of its application in the whirlwigs (Gyrinus), and some Ephemera, which have absolutely four * Philosoph. Ent. p. six, 4. THE HEAD. 63 eyes. In some of the Coleoptera, a corneous process originating at the clypeus (canthus of Kirby and Spence), either completely or partially divides the eyes, and these beetles, (Ateuchus, Geotrupes, Fabricius, &c. &c.) then appear to have four eyes. The genus Tetraopes, also, among the Capricorn beetles (Cerambycina), has apparently four eyes, from the antennae being inserted exactly in the middle of the long ovate eyes, and which thence seem divided into an upper and lower half. The SIMPLE EYES or auxiliary eyes (ocelli, oculi simplices, PI. VI, f. 8, B, stemmata, Kirby and Spence), are generally THREE in number, and more rarely we find but TWO. They are placed upon the vertex or upon the brow, most frequently in a triangular position ; they are much smaller than the true eyes, and consist of but one very convex case. They are found in all the orders of insects ; among the Cole- optera, indeed, only as exceptions *, in others, the Diptera, for example, very universally. The larvae of insects with a perfect meta- morphosis are destitute of compound eyes, and instead of them have mostly simple eyes ; in many instances they have none. THE ANTENNAE (Antennae). 72- The ANTENNJE must be distinguished as the third most important group of the organs of the head. They are two jointed organs, one of which is placed upon each side of the head between the angle of the mouth and the eyes. They appear never to be wanting, and there are never more than a single pair present. In some parasites only (Plulop- terus, Docophorus), there is close to and in front of each of them a small moveable stalk, which Nitzsch has called the little BEAM (trabeculus). It is different in the classes nearest to that of insects, the Crustacea, Myriapoda, and Arachneodea ; in which we find sometimes none, sometimes only two, and even four, or six antennae. As the differences of antennae are very great, we must divide our consideration of them under several heads. These are their situation, relation to the body, their general construction, construction of the individual joints, and their clothing. * Germar discovered them in Omalium ; they were afterwards discovered in Antho- phagus and Paussus. A very particular observer, on the contrary, Straus-Dtirckheim, denies their being eyes, although he does not dispute the existence of the points, page 58. PARTIAL ORISMOLOGY. 1. Situation of the Antenna 1 . FRONTAL (ant. frontales}, they are called when they are inserted directly upon the brow (Bees, PL VI. f. 8, c, c). PREOCULAR (ant. prceoculares}, are such as are inserted close to the front of the eyes (Carabus, PI. III. f. 11 and 13, y, y, y). INTEROCULAR (a. interoculares), when they are placed between both the eyes. EXTRA-OCULAR (a. extra-ocular es), when placed very distant from the eyes. INOCULAR (a. inoculares), when the eye surrounds the base of the antennae (Cerambyx). INFRA-OCULAR (a. infra-oculares), when inserted beneath the eyes. When they are placed, as is usual, upon the upper part of the head, they are called SUPERIOR (a.superiores); but when beneath, INFERIOR (a. inferiores). When their basal joints are inserted very closely together, they are called APPROXIMATE (a. approximates) ; but when they are wide apart they are styled DISTANT (a. distantes). 2. Relation of the Antennae to the Body. ELONGATE (elongates), when of the same length as the body (Lep- tura). LONGER (longiores), when longer than the body (Saperda). VERY LONG (longissimce'), when they are considerably longer than the body (Lamia cedilis), Fab.). SHORT (breves'), when about the length of the head. SHORTER (breviores), when they are longer than the head, but shorter than the body. VERY SHORT (jbrevissim.ce}, when not so long as the head. 3. Forms of entire Antennae. Antennae which entirely consist of equal joints are called EQUAL (equales), whereas those whose joints are dissimilar receive the name of UNEQUAL (inequales~). Both kinds are subjected to various differences, which we will now proceed to consider. THE HEAD. n. Equal Antenna. SETACEOUS (setacea, PL VII. f. 1), are such which very gradually decrease, becoming pointed at the apex (Locust a, Fab.). SETIFORM (setiformes, PI. VII. f. 2), when it resembles a slender, short bristle which springs from a thicker basal joint (Libellula}. This form is distinguished from the SUBULATE (subulata, PI. VII. f. 3), by the latter being shorter, thicker, and slightly bent (Leptis"). FILIFORM {jiliformes, PI. VII. f. 4), when of the same thickness throughout, and composed of cylindrical joints (Carabus}. MONILIFORM (moniliformes, PL VII. f. 5), is when the joints are globose (Tenebrio). ENSIFORM (ensiformes, PL VII. f. 6 h when the joincs are com- pressed, and have a sharp edge on each side (Truxalis}. FALCIFORM (falciform^, PL VII. f. 7), when arched like a sickle. DENTATE (dentatcs, PL VII. f. 8), when their joints are armed with slight, pointed spines (Stenochorus). SERRATE (serrata, PL VII. f. 9), when the joints are triangular, and are so arranged that the prominent angle is placed anteriorly, and inclines downwards (Elate)-}. BISERRATE (biserratai), when a similar angle is also placed upwards, and, when so, the point of insertion of the joints is not at the superior angle, but at the centre of the base of the triangle. In the latter case, the joints of the antennae form an isosceles triangle, whereas in the former they are more or less rectangular. IMBRICATE (imbricate, PL VII. f. 10), is when the joints are conical, but deeply excavated, so that one joint is inserted half way within the other (Prionus}. PECTINATE (pectinate, PL VII. f. 11), when the joints have long processes on one side, like the teeth of a comb. BIPECTINATE (bipectinatce), when such a process issues from each side of the joint (Lopkyrus} ; or DOUBLY PECTINATED (duplicato-pectinatce, PL VII. f. 12), when there are two processes on each side of the joints (Ctcnophora). CIRRATE (cirratce, PL VII. f. 13), when the branches of such doubly or singly pectinated antennae are very long and curled, and sometimes, but not always, fringed with hair. DISTICHOUS (distichtz'), when the processes originate from the apex of the joint, and do not incline at right angles towards the sides, but bend for- ward at acute angles. FLABELLATE ( fiabellatce, PL VII. f. 14), F 66 PARTIAL ORISMOLOGY. are pectinated antennae., whose joints are very short , but the processes are very long and flat, and consequently lie close together. BIFLA- BELLATE (biflabdlalce) , when both sides of the joints send forth such processes. BRANCHED (ramoscp}, when some of the joints only send forth pro- cesses upwards (PI. VII. f. 15). This form should, by rights, be placed under the following head ; but as they are in general filiform antennae which are furnished with such appendages, and they con- sequently bear great resemblance to the preceding forms, we have preferred introducing them here, among those they were most like. FORKED (furcates, PI. VII. f. 16), is when throughout its whole length it is separated into two branches or prongs (Schizocerus, Lat.). b. Unequal Antennae. THE inequality of antennae proceeds chiefly from the differing form of their second and last joint, on which account they demand especial notice. Very generally the first or second joint is much longer than the following, and is also not placed in the same direction with them, but the third joint is inserted laterally upon the second at a right angle. Such antennae are called BROKEN (fractal), or GENICU- LATE (geniculatte, PI. VII. f. 17) ; and the long joint is distinguished as the SCAPE (scapus, the same, a~), and the following as the BRANCH (flagelhim, the same, b). The branch of such geniculated antennae is frequently merely cylin- drical or filiform (Apiuria, fig. 17) ; in other instances, on the contrary, the joints of the branch differ again from each other. We thence dis- tinguish many forms which are also found in not geniculated but merely unequal antennae. The following are of this description: CLAVATE (clavatce, PI. VII. f. 18), when the joints become gra- dually broader, so that the whole organ assumes the form of a club (Silpha). CAPITATE (capiiatce), or such whose terminal joint forms a large round knob. If the knob is formed by but one joint, it is called SIMPLE (capitulum solidum}; but when composed of several, it is called, in contradistinction, COMPOUND (capitulum composition, PI. VII. f. 19, Necrophorus). PERFOLIATE (cap. perfolialum) , when the joints of the knob slightly stand off from each other all round (Hydrophilus, THE HEAD. 67 PL VII. f. 20) ; LAMELLATE (cap. lamelhitmn), when the joints of the knob extend on one side into broad leaves (PI. VII. f. 21, Melolontlia) ; TUNICATE (cap. tunicalum), when each successive joint is buried in the preceding funnel-shaped one (PL VIII. f. 1, Lethrus} ; INFLATED (cap. iiiflatum), when the knob has the form of a broad bladder (PL VIII. f. 2, Paussns) ; SPLIT (cap. jissuni), when the joints upon one side are divided as by incisures (PL VIII. f. 3, Lucaims). HOOKED (imcinatce], when the last joint bends back upon the preceding (PL VIII. f. 4, the male of Odynerus}. NODOSE (nodosce, PL VIII. f. 5), are those antennae which have their intermediate and terminal joints thicker than the remainder (many Curculios). ANGUSTATE (angustatte), on the contrary, when the middle joints are thinner than at the beginning or the end (PL VIII. f. 6, Asilus). SETIGEROUS (seligerte), are such whose terminal joint has upon its upper side a fine BRISTLE (seta). The bristle is either SIMPLE (sim- plex, PL VIII. f. 7), or PLUMOSE (plumosa, PL VIII. f. 8, Volucdla), when upon each side it sends forth fine and delicate branches. These forms are in general only found in the three-jointed antennae of the Diptera, the very various forms of which are shown in the figures 6 to 17 of the eighth plate. MUCRONATE (rnucronatts), are those whose last thick joint suddenly terminates in a sharp point (PL VIII. f. 18, Empis). AURICULATE (auriculatce), are those antenna? whose inferior joint is distended into a concave plate, not unlike the shell of an ear, and which partially covers the rest (PL VIII. f. 20, Gyrinus ; f. 19, Parnus). IRREGULAR (irregulares), lastly, are all such antennae, all or several of the joints of which aue dissimilar in form to eacli other (PL VIII. f. 22, Cerocoma ; f. 30, Agaon). 4. Number of the Joints, Antennas which consist of but ONE joint are called EXARTICULATE (exarticulat/j.iov signifies a small shoulder. THE THORAX. 77 peculiar (for example, the Cerambycina'), the superior plate is united to the inferior without the indication of any separation, so that the parts distinguished in the former can be regarded in these only as regions. The prothoracic case has, besides the feet, no other limbs or peculiar appendages, with the exception of two instances. In the one, we observe a moveable spine on each side of the prothorax, (Acrocintts longimanus} ; the second instance is found in the family of the Rhiphidoptera*, on each side of the prothorax of which a contorted and twisted corneous appendage is attached. All other prominences of the prothoracic case are integral portions of it, and are to be considered only as processes. There is a multiplicity of them and of the most distinct forms, the families of the Lamellicoriiia and Cicadaria display the most remarkable. The PATAGIA (patogia) of the Lepidoptera, which Kirby and Spence consider as appendages of the prothorax, are not seated upon this, but upon the mesothorax. 75. In those orders in which the prothorax is in closer connection with the mesothorax, we often find analogous parts ; but it just as often forms, as well as the whole thorax, one entire piece, upon the superficies of which the different parts are indicated by means of deep impressions and furrows. This is the case in the Diptera and the Neuroptera ; for, notwithstanding the distinctness with which the different thoracic plates are marked out, for example, in the Libellulina (PL XI. No. 3, f. 1 3), they are, nevertheless, h'rmly attached together, and require considerable force and art to separate them. In the Hymenoptera, this separation is not merely indicated, but it actually takes place. A small corneous plate with two sockets, and seated quite in front of the pro- thorax, represents in this order the prosternum (PL XII. No. 1 and 2, B, B, B.) ; a larger plate, which has a narrow margin, and which, descending perpendicularly, bows round and extends on each side to the origin of the wings (the collar of Kirby), takes the place of the pronolum (PL XII. No. 1 and 2, A, A.). Kirby and Spence con- sider this plate as an integral portion of the second segment, and confirm themselves in this view of it by its generally remaining attached to the mesothoracic segment when the first pair of legs are separated from the prothorax. They, consequently, think they have observed * Strepsiptera, Kirby. 78 PARTIAL ORISMOLOGY. that some insects (Fespa, Cimbex) possess both a collar and a prono- tum ; and that in others (Xylocopa), the collar forms a complete ring. Their first observation is perfectly correct, but not convincing; it frequently happens that the first segment of the thorax is more strongly affixed to the thorax than to the abdomen, and remains attached to the former when we wish to separate the latter (Hister, Gryllus, Gryllolalpa, &c. &c.); the same remark may be made with respect to the COXCB, and with still greater latitude, but which are, notwith- standing, joints of the legs : why should not, therefore, the pronotum occasionally be affixed more firmly to the second segment of the thorax than to the prosternurn ? The second observation is absolutely erro- neous ; for what Kirby and Spence consider as their prolhorax, (our pronotum), is sometimes the extended membrane of the neck (Fespa, Cimbex), sometimes a plate, as in the Libellulina, representing the anterior part of the mesonotum ; and which, in the Coleoptera, is covered by the pronotum. The third observation is also imaginary, for proportions of that kind are always the peculiarities of entire families ; and this conformation of the prothoracic segment is found as little among the rest of the bees as in Xylocopa. Whereas, on the contrary, the following reasons clearly prove this part to be the pronotum : 1st. In all those orders which possess a collar, the pronotnm would necessarily be deficient, as they possess no part excepting this which responds to it. On the other side these orders would have a cor- neous part more upon the mesothoracic segment than any of those provided with a distinct and free prothorax, in which we in vain seek upon the mesothoracic segment for a part analogous to the collar. 2ndly. That Kirby and Spence's collare is our pronotum, is proved incontestibly by the circumstance, that, upon its separation from the second segment, there is a spiracle. We observe this spiracle very distinctly in the Diptera (PI. XIV. No. 1, f. 2, a), which shows us very evidently the limits of the prothorax, for which, without this indication, we might look in vain, as the entire order is deficient in a clear separation of the plates of the thorax. (See also PI. XIV. No. 2, f. 2, .) In the Hymenoptera and Lepidoptera, this spiracle lies beneath the patagitim, and, in the former (Fespa, Scolia, &c.), appears as a distinct opening beneath the superior wing. This process, which forms a sort of flap, may be called TILE (tegula), for the organ which Kirby and Spence have so called is the same with their patagium THE THORAX. 'Ji) (PI. XII. No. 1 and 2, d, d ; see 77)- The first spiracle is constantly the property of the prothorax throughout all the orders which have this part free, and in a very flexible articulation with the second ; conse- quently, in all the remaining orders, the first spiracle of the thorax must necessarily belong to its first segment, and not, as would be the case were the collar a portion of the mesothorax, to the second thoracic segment. Srdly. We may even adopt, as proofs in our favour, the reasons cited by Kirby and Spence, in opposition to their own views. In the first place, they say the collar lies directly over the prosternum (Chlorion), and then moves freely with it (Pompilus, Chrysis), when the collar has no prophragma (see lower down) ; but which is found upon the dorsal piece lying behind it. Kirby and Spence have not refuted all these reasons, but have considered them as rendered ineffec- tive by their contrary reasons, which we have entirely refuted. It clearly appears to us, therefore, that the term COLLAR will, in future, be useless, and instead of it, this part must be called by its more appropriate name of pronotum. In the order of the Lepidoptera, this pronotum approaches to the shape of a collar, for in them it leans against the second segment, in the form of a thin plate, and thus forms its commencement (PI. XII. No. 1, f. 1, ). Besides which, it is here called collare by the describers of Lepidoptera, particularly wherever it is covered with differently coloured hair, or small scales. But even here it is the true represen- tative of the pronotum. 76. The intermediate ring of the thorax, the MESOTHORAX consists, in its most developed state, of seven pieces, the three pairs of which are so closely united, that each appears to form but one piece ; thence, consequently, we have four chief pieces, which we distinguish as MESO- NOTUM, MESOSTERNUM, and the SCAPULA. The MESONOTUM (PI. IX. &c. c, c, c. Kirby and Spence's dorso- lum and scutellum), forms superiorly the corneous covering of the mesotliorax. It is generally of a quadrate shape ; it is convex on the exterior and concave within, bent down laterally, and is here, chiefly* in direct union with the remaining corneous plates. It is divided into two parts, which are never distinctly separated, but merely indicated upon the superficices. The anterior piece or true back (dorsolum of 80 PARTIAL ORISMOLOGY. Kirby and Spenee), generally exceeds the posterior piece in size. In the orders with a free prothorax, this covers it, and it is only visible upon the removal of the latter ; in the rest it occupies the whole central sur- face of the back. In front, at its exterior angles, the corneous ribs of the superior wings articulate, and two corneous ridges, originating at this point and proceeding into the cavity of the thorax, serve for the inser- tion of the muscles which move the wings. In the Hydrocanthari, the mesonoturn is very small, and indicated only by a delicate corneous transverse line (PL IX. No. 2, f. 7, c.) ; it is very large in the Melli- force and Lepidoptera, as well as in the Diptera ; in the dragon flies, (PI. XI. No. 3, f. 1, 2, c, c.), it forms as an obliquely descending bent plate, the anterior portion of the thorax in front of the wings, and therefore does not represent the collar of the Hymenoptera and Diptera (our pronotum), as Kirby and Spence maintain. The posterior divi- sion, the SCUTELLUM (scutcllum), is here seated, as in all, between the wings. This SCUTELLUM (PI. XI. &c. c, c.), is, properly, no separated part ; but, as we have already seen, a mere process of the mesonotum. It is to be observed very distinctly in the Coleoptera, in which it presents itself as a small triangular plate seated between the elytra and the pronotum. In some genera (Macraspis), it attains conside- rable size; indeed in Tetyra and Chelyphus, it almost covers the whole abdomen *. It always extends far backwards, between the posterior wings ; and in many families, it completely covers the third thoracic segment (PI. XIII. No. 4 and 5, c, c. ; PI. XIV. No. 1 and 2, c, c.) ; not unfrequently a strong membrane or even a peculiar cor- neous ridge (Cicada, P. XIII. No. 5, f. 1, d, d.} proceeds from the side of the scutellum to the base of the superior wings, and thereby strengthens their connection with the dorsal piece (PI. XIII. No. 4, f. 1, d, d}. This ridge or membrane, Kirby and Spence call the frenum. In many Coleoptera the scutellum appears to be deficient, from its not displaying itself upon the superior surface between the elytra (as in Copris) ; but it is, nevertheless, present, although covered by the elytra and pronotum. These have been called Escu- tellati, wanting a scutellum. It is not unusual to find other processes upon the scutellum, as spines and teeth, and which are occasionally found in almost all the orders (Psi- lus Boscli, Stratiomys, Sargus, Reduvius). But we more rarely observe I * Compare Dalman, Analecta Entomol. p. 32, p. 2, B. THE THORAX. 81 such excrescences upon the mesonotum (Clilellarid'). The prominences upon the surface of the mesonotum (for example, in Cimbex, Sircx, Tabanus, Asilus, &c.) arise from the insertion of the muscles ; the furrows which separate them correspond with similar ridges upon the interior, which the bundles of muscles embrace. A great partition, of a horny substance, separates superiorly the cavity of the second thoracic segment from the first ; it descends from the upper side of the dorsal piece, in greater or less distension, and likewise serves for the insertion of the muscles of the back. Kirby and Spence call it PROPHRAGMA. At its superior edge the membrane is affixed, which unites the first and second segments. 77- The SCAPULAE are contiguous to the mesonotum (PI. IX., &c., D, D). On each side, in front, close to the mesonotum, they assist to form the articulating socket of the superior wings (pteropega, Kirby and Spence), and they here contract themselves, that they may pass into the cavities of the prothorax in those orders which have a distinctly separated pro- thorax, and with their opposite wing they pass down the sides of the mesothoracic segment. They consequently fall into two divisions, which may be distinguished as the anterior and posterior wings of the scapulffi (ala scapulae anterior et posterior). Beneath and beyond the posterior wings of the scapulae, in the Coleoptera, is found the spiracle of the second thoracic segment ; it is entirely covered by it, which explains why it has been hitherto overlooked. Straus- Durckheim dis- covered it, and has distinctly shown its situation*. My attention being thus drawn to it, I have fully convinced myself of its constant presence in the Coleoptera, by numerous investigations. In the orders with an unseparated prothorax, this part appears to diminish in compass as well as in importance ; at least we never clearly discern a distinctly sepa- rated scapula, but peculiar pieces, analogous by their situation, doubt- lessly represent them, although with an altered function. As such we consider the patagia and tegulce of the Lepidoptera and Hymenoptera ; they are both decidedly the same part, and are also seated precisely at the same place, but differ in their mode of attachment, the tegula of the Hymenoplera being affixed to the mesonotum above the wing, and the patagium of the Lepidoptera beneath it, to that part which we * C'onsid. (Jen., PI. VII. fip. 6, II. G 82 PARTIAL ORISMOLOGY. consider as the analogue of the posterior wing of the scapula (see PL XII. No. 1, f. 1 and 2, d; No. 2, f. 2, d). In the Diptera, this scale appears as a mere protuberance (PL XIV. No. 1, d) in front of the base of the wings ; thus also, by reason of its smallness in many of the Hymenoptera (punclum callosum ante alas of Fabricius) ; but in these it is always a separate piece. That which has been called the SHOULDERS (humeri) in other Diptera, for example, in Myopa, is certainly erroneous, for it is the analogue of the collar e of the Hyme- noptera, and the same as our pronotum (PL XIV. No. 2, A). In all the apterous genera, as well as in all those orders which display a closer union of the several pieces of the thorax, the scapulae are not either to be recognised as distinct pieces. In the Coleoptera and Orthoptera they are never wanting ; but their separation into two parts, which we have called their wings, is not always apparent. The third piece, the MESOSTERNUM (peristethium of Kirby and Spence), is, as well as the scapulae, divided into two parts ; but here they are equal. It is directly opposite to the mesonoium, upon the underside of the thoracic case, and includes one-half of the acetabula of the intermediate legs. It is distinctly observed in all the orders; in many (Diptera, Hemiptera) it is not separated from the other pieces by clearly defined limits, but merely indicated by furrows ; in others (the Hymenoptera), it attains considerable size (PL XII. No. 2, f. 2 and 3, E, E), and in these extends upwards upon the sides of the thoracic case, as high as the articulation of the superior wings. In the Coleoptera and Orthoptera, which display considerable resemblance in the conformation of their thorax, it is small, and frequently appears but as a small prominent ridge between the intermediate legs (Hydro- philus, GryllotaJpa, PL IX. No. 1, f. 8, E) ; in the former it is sometimes even excavated for the reception of the dagger-shaped process of the prosternum (Elater, Buprestis, PL IX. No. 3, f. 5, E ; Dyticus, PL IX. No. 2, f. 8). This sternum is separated into two equal halves by a central longitudinal division, which, however, is but little apparent upon its superficies, and can be discovered only upon a close inspection (Buprestis, Dyticus, &c.). 78. The third and last segment of the thorax, the METATHORAX, resem- bles the second, in being of a more united structure than the first, THE THORAX. 83 -which is to be ascribed chiefly to the circumstance of their having both wings and legs attached to them, whereas the first has but legs alone ; consequently greater compass was required for the reception of the muscles of the wings, and which explains the reason of their much more artificial construction. We likewise observe the fullest development in the number and situation of the parts to occur here, also, in the Cole- optera, as was to be expected in the highest order. The third seg- ment, likewise, consists of seven pieces, which are similar to those of the second. The superior central piece, the METANOTUM (PI. IX., &c. p, F), occupies the whole superior part of the metathorax ; it is generally an oblong quadrangle, with the anterior angles advanced : it is frequently hollowed in front. A somewhat arched partition (mesophragma of Kirby and Spence), which descends into the cavity of the thorax, sepa- rates the cavity of the meso- from that of the metathorax, and serves for the insertion of the muscles of the back, as well as of the legs. The membrane which connects this segment with the preceding passes over this partition, but which is, however, no longer apparent in the Hymen- optera, and in all those orders wherein the corneous plates are attached together. In general, the posterior edge of the SCUTELLUM projects somewhat over the anterior margin of the metathorax ; it often (Diptera and Cicadaria) conceals its centre though rarely its entire surface (Tdbanus, Pi. XIV. No. 1. c; Cheh/phus, Tetyra). Sometimes a straight furrow, which, however, occasionally runs concentrically with the scutellum, separates from the remainder an anterior portion of the metathorax, which has been called POSTSCUTELLUM. In the saw-flies (Tenthredonodea) this portion, particularly laterally, very strongly projects, and displays two small, very generally white, points, which are called CENCHRI. The posterior wings are placed at the anterior angles, and often occupy the whole sides of the metathorax. This occurs through the medium of a peculiar organisation, the description of which belongs to the anatomical division ; thus much may stand here the strong cor- neous nervures are attached to the metathorax by articulation, and the membrane is formally affixed to it, and is supported, upon the expansion of the wing, by the horny plates contained within it. A pergamenteous partition at the posterior margin, and called the METAPHRAGMA, and which descends in a perpendicular direction, bowing in its middle towards the abdomen, separates the latter from G 2 84 PARTIAL OR1SMOLOGY. the thorax (PL XIV. No. 1, f. 2, H); there remains only a small space below for the passage of the intestines, the organs of the nervous and respiratory systems, and of the vessels, &c. In all insects with a pedunculated abdomen (abdomine petiolate), this partition is exposed, and thus forms the covering of the truncated posterior portion of the metathoracic segment; it even seems to distend itself towards the superior surface, and to terminate only at the above indicated furrow of the metathorax, whereby this becomes a positive suture (PL XII. No. 2, f. 1 and 2, Scolia and other Hymenoptera). Directly opposite to the metanotum, and precisely in the centre of the under surface, we find the METASTERNUM (PL IX., &c. G, G) ; likewise very generally a quadrate, corneous plate, but which more rarely takes the shape of a triangle, hexagon or octagon (Hisler, PI. IX. No. 3, f. 12, G), and which helps to form anteriorly the aceta- bula of the intermediate legs, and, posteriorly, those of the posterior legs. It is sometimes perfectly flat, sometimes slightly convex, and sometimes distinctly ridged, and occasionally prolonged posteriorly into a point (Xiphus metasterni) ; arid when thus, it projects over the abdomen (Hydrophilus). It differs considerably in extent in Qryctes (PI. X. No. 2, f. 4, G) and Cetonia (the same, No. 1, f. 2, G) ; it occupies nearly the whole pectus ; sometimes, as in Hister (PL IX. No. 3, f. 12, G), only the centre ; sometimes it is compressed into a comparatively small compass by the coxce of the posterior legs ; it is thus formed in Dyticus (PL IX. No. 2, f. 8, G). In many Coleop- tera, for example, in the Lamellicornia, the meso-and meta-sternum are so closely united, that it requires violence to effect a separation. In others (for example, Buprestis, PL IX. No. 3, f. 5, G), the metasternum consists of two halves, which are separated by a central longitudinal suture, which internally forms a ridge. The construction in the other orders differs materially from this description of it in the beetles ; but in the Orlhoplera very slightly. In these, likewise, the metasternum is a clearly distinguishable, but undivided plate, placed between the acetabula of the four posterior legs (PL XI. No. 2, f. 5, G). In the apterous genera, we do not observe the meso- and meta-sternum to be divided into several pieces, and they adhere tolerably closely to the original annular form of the segments (see PI. XIII. No. 1 and 2, the thorax of the female Tengyra and Myrmosa). In the Uymenoptera, the construction of the meta- THE THORAX. 85 sternum closely approximates to the above description of that of the beetles ; it is likewise seated between the acetabula of the posterior legs, and appears as a distinct, but undivided plate, as in Scotia (PI. X. No. 2, f. 2 and 3, G). In the Lepidoptera it takes the figure of a semicircle, which lies in front of the coxse of the posterior legs, separates them from those of the intermediate legs, and between them it projects, with its obtuse ends, at the sides of the thorax (PL XIII. No. 4, f. 2, G). It appears indicated in the same situation in the Diptera, but is not separated, for in them all the parts of the thoracic segments are firmly united. In the Hymenoptera, the metasternum merits particular atten- tion, from its deviating from the structure of the other orders by pos- sessing a spiracle peculiar to it, which is placed anteriorly upon its supe- rior lateral margin (see PI. XII. No. 1 and 2, f. 1 and 2, ft). In the Lepidoptera and Diptera, it is placed as in the other orders, between the meso- and meta-thorax. Latreille, therefore, considers this portion of the thorax as belonging to the abdomen, maintaining that no spira- cles are to be found upon those segments of the thorax which are provided with wings ; which assertion is, however, unfounded, as we have seen. He thence concludes that the halteres (see the end of this section) of the Diptera cannot represent the posterior wings of the other orders, because a spiracle is found upon the segment where they are placed. But that this circumstance proves nothing will have become self-evident. Between the metanotum and the metasternum, two other horny pieces are found on each side, which we, with Kirby and Spence, distinguish as the PLEURA and PARAPLEURA. Straus calls them ISCHIA, and distinguishes the former as the ischium primum ; the latter as ischium secundum. The PLEURA (PI. IX. No. 2, J, j) is contiguous to the metanotum, and is united to it by a delicate membrane ; the membrane of the wing proceeds from it, and this is attached in the same manner to the pleura beneath, as it is affixed above to the metanotum. It is a small, longi- tudinal, scarcely observable plate, which, in repose, is covered by the elytra, and is not perceptible until they are removed. In the Orthop- tera (for example, Gryllotalpa, PI. XI. No. 1, f. 8, j), the pleura is much extended, and posteriorly it is drawn somewhat downwards, so that it extends to the acetabula of the posterior coxae. In the Libellu- lina, it is almost supplanted by the very large parapleurse, and in these 80 PARTIAL ORISMOLOGY. insects, from the two pieces being united posteriorly, it appears as a small triangle* beneath the cavity where the abdomen is affixed (PI. XL No. 3, f. 3, j). In the Hymenoptera, Lepidoptera, Diptera, and Hemiptera, the pleurae and parapleurse are not distinctly separated, but form a single, undivided pleura, which often, besides, is strictly united with either the metanotum or metasternum, or indeed with both together. The PARAPLEURJE (PI. IX., &c. H, H) of the Coleoptera, as well as of the other orders in which it is distinctly found, lies between the meta- sternum and the pleura. In general, they are larger than the latter, lie nearer the under side of the body, and adapt themselves in shape to the space left by the other plates. They are very frequently quadrate (PL XI. No. 1, f. 6, H; No. 2, f. 10), with sometimes parallel, and sometimes diverging sides (PI. IX. No. 3, f. 6, H) ; in other cases, three- sided (PI. IX. No. 2, f. 8, H) ; and very large and trapezoida lin Gryl- lotalpa (PI. XL No. 1, f. 8, H), as well as \nLibellula (No. 3, f.2, H). In these they are prolonged posteriorly, make a bend at the angle of the thorax, and in the centre of the metasternum they unite in one piece (PL XL No. 3, f. 2 and 3, H). In the other orders, the pleurae and parapleurse are not separated, but form one single plate. In the Diptera peculiar interest attaches to it, from the remarkable halteres being seated there. They originate frequently in a stalk (stipes], as fine as a hair, from the anterior margin of the pleurae, and shortly terminate in sometimes a round, and at others a compressed knob (capitulum). They frequently stand quite free, and are then called NAKED (halteres nudi), or else they are covered by one or two delicate SCALES (squama}, which are attached to the mesothorax, and extend from its margin upwards to the scutellum, and are doubtlessly analogous to the previ- ously described frenum of the other orders. We have not yet attained any very distinct idea of the import of the halteres ; but this is not the place to introduce an investigation of the subject ; we refer to the proper place, in the second and third divisions, for much that applies to it. * Without this somewhat forced view, it would be scarcely possible to explain the construction of the thorax in the Libellula. We must imagine the feet to be drawn forwards, whilst the back and the wings project posteriorly, whereby the parapleurae are advanced in front of the pleunc, and these united posteriorly into one piece. THE THORAX. 87 78 a. After having thus explained the construction of the thorax in the different orders of insects, it remains for us now to notice the works of other naturalists upon the same subject, and to indicate the differ- ence of the results of their investigations. The earliest work of this kind is that of Chabrier ; it appeared as the introduction to his treatise upon the flight of insects *, which was presented to the academy of Paris on the 28th of February, 1820. He here, with Latreille, divides the thorax into protliorax, mesothorax, and metatliorax, but unites the two last divisions as tronc alifire. Each of these segments is subdivided into the upper, or DORSAL, and under, or PECTORAL, part ; called also conque pectorale, from which processes, the entosternum, spring inwards. Between both, upon the metathorax, are found the clavicules thoraciques ; and upon the meso- thorax, the plaques fulcr ales. The partitions, or phragmae, he describes as prce- and post-dorsum ; and he calls the scutellum, bascule. He consequently adopts as many pieces as we have described : the annexed table will show more distinctly their conformity. Chabrier was succeeded by Audouin in a similar investigation, in which, however, the chief object was the particular description of the sternum. This was also presented to the academy, and a report of it was given by Cuvier, in the Annales Generales de Physique, torn. vii. (1821 f ). He has here adopted, in general, the same parts; but each single one is divided into several pieces, with particular names, although such pieces are never found separated from each other. It may also be objected to Audouin's performance, that he has not distinguished the several dorsal and pectoral plates of the three segments by distinct names, but has merely called them terga and pectora. We cannot, therefore, retain his nomenclature. But Audouin admits of three seg- ments, which he calls pro-, meso-, and meta-thorax ; each consists of tergum, episternum, sternum, and entothorax ; to which are added, in the prothorax, the trochantinus and the peritrema ; in the meso- thorax, the peritrema and paraptera ; and in the metathorax, the parapterum only. Each tergum consists of the preescutum, or the anterior deflexed margin, which, in the mesonotum, becomes the pro- * Essay sur le Vol. des Insectes. Paris, 1 832, 4to. t Audouin himself published the paper in the Annales des Sciences Naturelles, torn. i. p. 97, and p. 416. 88 PARTIAL ORISMOLOGY. phragma, and, in the metanotum, the mesophragma ; the scutum, the disc of each dorsal plate ; the scutellum, or the posterior margin; and the postscutellum, the posterior deflexed margin, which, in the meso- notum, becomes sometimes the mesophragma, or, upon the metanotum, it forms itself into the metaphragma. Upon the prothorax, the epister- num and the epimeruin form our omium : the former is the exterior surface ; the latter the interior surface, directed towards the acetabula. Where the shoulder- piece is not free, they then belong to the pronotum, and form the lateral parts. The trochantinus by no means belongs to the thoracic case, but to the coxae ( 168, II. 4) ; the same applies to the peritrema, which forms the corneous ring of the spiracle. The entothorax is what we shall describe below ( 165) as the processus internus sterni ; it is in strict union with the sternal plate, and is never free or separated from it. I do not distinctly know what the parapterum is ; probably a lateral process of the dorsal plate. I have never found a free portion in that situation. In the mesothorax, the episternum and epimerum are our scapulae : but upon the metathorax, the parapleurse. After Audouin, Straus-Durckheim * and Macleay f both produced, nearly about the same time, a work upon the thorax of insects : the description of the latter adheres very closely to that of Audouin. He uses the same names and adopts the same parts ; but in his sub- division of them, he goes still further, without there being a sufficient reason for it. For example, the sternal plates of the meso- and meta- thorax, he says, consist each of eight pieces, although in no insect with which I am acquainted is there the least indication of any other sepa- ration than the above-adduced division into two halves. Straus-Durckheim pursues in his description of the thorax, as well as throughout his work, a peculiar path, without troubling himself in the least about the labours of his predecessors. He divides the whole thorax into corselet and thorax, the latter comprising that portion which bears the wings ; this is again divided into prothorax (our mesothorax) and metathorax. The corselet consists of the bouclier, our pronotum ; the two pubis, the rotule, Audouin's trochantinus, and the sternum antcrieure. He distinguishes in his prothorax the ecusson, our mesonotum,, the clavicule anterieure, Audouin's para- " Consid. Gen. sur TAnat. comp. des Alii. Articiil. Par. 1828, 4to. p. 76, &c. f Zoological Journal, Vol. v, (1830), No. 18, p. 145. THE THORAX. 89 pterum, a part unknown to me ; the ties or ilialiques, our scapula, and the sternum moyen, our mesosternum. His metathorax consists of the clipeus, our metanotum ; the clamcule posterienre, a part which I also could not find, and which I consider to be either a mere process of the metanotum, or one of the joint pieces at the root of the wing ; the two ischion, our pleura and parapleura ; and lastly, the sternum posterieure, our metasternum. He also takes notice of the corneous rings of the spiracles, as parts of the thorax, and which are seated in the articu- latory membrane of it : he calls them cadres. The description is good and praiseworthy? like all the works of the skilful Straus ; but the French names which he adopts must give place to the partially older Greek ones. In a comparative view of the number of the thoracic pieces named by different authors, we find that Knoch has twelve, Kirby and Spence, twenty, Chabrier and myself, eighteen, Audouin, thirty-six, of which Macleay makes fifty-two, by the separation of each dorsal plate into four pieces ; and Straus-Durckheim, twenty-two, because, besides the eighteen described ones, he adopts a clamcule to both the meso- and meta-notum. The annexed table gives a precise comparative view of the nomen- clature of the several writers. COMPARATIVE VIEW OF THE NOMENCLATURE OF THE SEVERAL AUTHORS, FOR THE PARTS OF THE THORAX AND THEIR PROCESSES. & * a y c!> 1 (/] S A -s -S3 O ^*> a ~ S S C . J^ r- _g a 5 1 '!> c o "C 11 cu ^> . c ~ sgc? Ill El ^ -s 8 M h .;=^;a o .,,, SK.C S=~~s ^Sssg to NOMENCL THE A PROT 1 E 3 S. 8 d, O rochantinu 'os termini, rocessusin igma primi MESOT "S* +j "-''c o s ^ ? -H U C ' a S 3 ? urn:* 5 4: OJ 4-* ^ ^ 2* < a g 1 if S i2 S 1 g'^S'^J . S J3 3 S ^ ^ W CC '*** O *^ ^ *"* f~ ^J jr p 4 tfl jj c * 5i i iJ 2 r~ *M QJ m^jJ^^J^ t* Ci~"^*^i> ws a^sss 1 fc =i-g ?< as T v *r' 1 ,***lfi 1 lalfe- uinj a, ,^g -Sag-,:^ j / A s^- f- 1 OH C/3 OnOS3J\T2n 30S VI s -OUB^OH ^-, S S S O E-i S -~v ^J ^ ^J --; -^ g B h' | !>< -^ Qj 1 II III 15 1-8 a g l * II & wl i s - 1 1 pli u Q CORSELE ." ? .2 b s ^j <* PS -2 , *S?.j ^ S^=- PliOTHOR ^> *^ ^ 1 ^ _S 5._a J v. Iverxe c liijues Posterirttr Cadres sec id.) as/ii/dodi ariom uiniu. 1 O a " . w s ^ -i, - s . gr ^t ^ S; = l lll?l-c iLJllt i^ill IS =5$ i -*- o ^ c g -c: ?: l^'-s i C c T- MESOTHORAX. = _ e;| 1^ 1 ^ SS " H "w 3> 5. w S. S 1 }5 t -^ "*"* S i S * ^ lunajj PeHMme second. Sternum (second). entotltorux. ^ . . S ji S ^ 1 Oa a '^5 Sg tc s? s-'S -S ? h-S^S^S -S -2 ^J ^ : ; ^ s c r ^ .R. s S fiSc^^2 ^^ W Cd ^ s ~ f. ./- J ^- y. Z: s '-J 2 f ^S^-13 '^ na ld 3?^ !*. *" !^axKl S^ >= S Ei co a, mn.uj,, S>l)39J mnS-taj, -snjyaj v^ !L> ' 11 X v -_ i , ' Ul O ^ J O - M X ."S - ^ ^o CHABRIER. PROTHORAX tie supe'rieure, o >llier. g^ !i " MESOTHOR; w S "s *? S * ec C 5J B.-0 Cltiincule t/inra- cii/ue. Sometimes in t parts. Coin/ite pectornl entosternum, furculiiire. ^ 5 S S ~ ? " N N ^ h g|-c 11 < S.&3 ^5l'~SO!j 5j 5C S 2 s 2 S a s S 5 f^ a. a. a. ^ &, ^ t=] *~~ / ~> _ | S ^ -mns.iofi S^ O j 5 S a, 'HHtfjII'IV X,tV3KO' i fS no suSJnV 3XOHJ, W O3 ITRUNCUS. 4J CO a 3 a | sg 2 5 i =s S 3 ^ ^ !- <*" 1 S . 03 ;> < t/^ K cS "3 S 60 C ci /- prophragma. ) dorsolum. j scutellum. ila. Scapularium. Peristethium. ( medifurca. a s '& z iiji rt . ij i rt'o'S cs " a t. K jj j g u 3 g f-llg 1 S "S g^ g S^-Sw S 0<5 S K w cj s o a aaaa s s s (^ s *^T "7" _y ca ^ ^^ J ^ \~ oadipaj^ x-BjomB^apj .' , 1 Aj S snj -omoj,j oada^uy 3Mf Hxnv a o 2S c oc o JJ O J. ^ & V V ' ' , ' ' v ' s S f g s o o d "3 4-J 3 F. J 3 a s 3s Iz; O M 3 o /-' 15 S -S S O e ta ^_ ^^ .. j-.,-^j 5 3.2 2 1 JS - ^ / ' S A cS >S f-> M^imSJOQ BrndB.ig a. ex, 'tunsjoQ p j *c ^* ^--v >3d THE THORAX. 91 ORGANS OF MOTION UPON THE THORAX. A. The Wings. 79. The organs of motion are of two kinds, either WINGS (aloe}, or LEGS (pedes~). The wings, generally four in number, are placed, as we have already seen, upon the second and third segments of the thorax, and united to it by means of joints or an articulatory membrane. They always consist of a double membrane, which is traversed by corneous VEINS or RIBS (jieurcg, vence, costte^), and by means of which they are held expanded. This, their general structure, suffers a variety of modifi- cations in the different orders, which may be comprehensively repre- sented in the following table : I. Four wings. 1. All of similar structure and membranous : A. Of equal size. Neuroptera (with the exception of the families of the May-flies), as well as the families of the Libellulina and Termitina. B. Of unequal size. Hymenoptera, Lepidoptera, Phryga- neodea, the remaining Dictyotoptcra, and many Hemi- ptcra homoptera. 2. The anterior corneous or pcrgamentaceous, the posterior membranous : A. The anterior corneous. a. Entirely corneous, Coleoptera. b. Half corneous, half membranous, Hemiplera heteroptera. B. The anterior pergamentaceous. Orihoptera, and some Hemiplera homoptera. II. Two membranous wings. Dipicra. The general observations which we purpose here introducing upon the wings, will merely refer to their number, situation, form, and clothing. The inquiries into their structure, import, and purpose, belong to other divisions of this work, and will, consequently, remain untouched upon here. Very little is to be said upon their number ; sometimes, and indeed, in certain genera and species of almost every order, they are wholly 92 PARTIAL ORISMOLOGY. deficient, more frequently only the posterior pair : thus, in all the Diptera, some Cimices and many Coleoptera, but in the majority of cases there are four distinct wings present. The deficiency of the first pair has never been observed. Their situation is more certain than their number, for wherever we find wings, they are attached to the second and third segments of the thorax, and, indeed, at its superior exterior dorsal edges, close to where the dorsal and lateral plates adjoin. If we find no wings here, we can speedily convince ourselves whether the insect does not possess them, or whether it has lost them by some casualty, which is not of unfre- quent occurrence. We speedily detect such a mutilation by the presence of the joint sockets and a portion of the wings. Apterous insects entirely want the sockets. Before we proceed to the consideration of the form of the wings, we must remind ourselves of the differences indicated in the preceding table, as they exercise an important influence upon the form of the wing. The horny or pergamentaceous anterior wings, namely, differ so considerably in their whole structure from the membranous poste- rior wings, that they have been very justly considered as different organs, and have been called the WING CASES (Elytra). The whilst the beetle, or any other insect which possesses elytra, reposes, they lie parallel beside each other upon the back and abdomen, and thus conceal not only the posterior wings, but also very generally the whole abdo- dem. It is from this function that they derive their name. We distinguish in the elytra their BASE (basis), the part by which they are attached to the thorax, and the opposite extremity, the APEX : then the MARGINS and the inner ones, which lie contiguous, and which we call the suture. Should the posterior wings be wanting, the union of the elytra is generally so strict, that it requires great force to sepa- rate them ; such elytra are called CONNATE (Elytra connata). The angles are thus distinguished, the superior exterior one, as shoulder angle (angulus humeralis), the interior one, as the angulus scutel- laris. The most usual form of the elytra is the longitudinal extended, we might almost say oblong, did not the exterior bowed margin very generally join the sutural margin, a ta pointed angle, or by its rounding very gradually pass into it. The upper surface is convex, the under concave ; the exterior margin is very generally deflexed, and often forms on the exterior a sharp edge. THE THORAX. 93 The following are the chief differences of the elytra: TRUNCATED (truncata), are such elytra which are a little shorter than the abdomen. ABBREVIATED (abbreviata), when they cover but a little more than its half. DIMIDIATE (dimidiata), when exactly half as long as the abdomen. SHORT (brevissima), when they are not half the length of the abdo- men. MUTILATED (mutilata), are those which cover only a portion of the abdomen, yet more than the half, but less than the apex ; they are, consequently, longer than the SHORT and shorter than the TRUNCATED elytra (Aptinus}- FASTIGIATE (fastigiatct), are such which extend a little beyond the apex of the abdomen. ENTIRE (integra), when they are exactly the length of the abdo- men, and display no distinguishing peculiarity of form. AURICULATE (auriculata), are those which have at their humeral angle a peculiar, free appendage (Lycus, Cassida.) SUBULATE ( subulata}, are those which gradually decrease towards their apex, and which leave, both upon the sutural and exterior margins, a portion of the abdomen uncovered (Necydalis, Fabr.) ELONGATE (elongata), are those which are much longer than the abdomen. DEHISCENT (dehiscentia), when the suture is somewhat divergent at the apex. AMPLIATE (ampliata, .<:. amplificata), when the edge of the exte- rior margin is very high and prominent (Dyticus latissimns.) . COMPLICANT (complicantia) , when one elytra extends over the other, and partially covers it (Meloe). According to their inclination we distinguish EVEN (piano) elytra, the whole superficies of which is upon one plane. DEFLEXED (deflexa], when the vicinity of the suture lies higher than the exterior margin ; sometimes they rise into a pyramid, called TURRETED (turrita), or they are very convex in the centre, viz. GIBBOUS (gibba). Both the elytra together are called the sheath or covering (coleop- tera), and each single one a wing case (elytrum). The differences of surface have been already sufficiently described at 94 PARTIAL OIUSMOLOGY. section 19, for almost all the differences of form there named are to be found in elytra. The same applies to the differences of margin, but with greater limitation. Their clothing, also, is so variously different, that scarcely any description of it is found upon the insect body, which does not also occur upon the elytra ; we, therefore, here again refer to the General Orismology. The hemelytra, or half corneous wing-cases of the Hemiptera heteroptera, have most qualities in common with the entirely horny elytra. In the majority we can distinguish four divisions separated by furrows, the first three of which are horny, but the fourth forms the membranous portion. The first, the NAIL, ( Clavus, PI. XV. f. ] . ), is a longitudinal almost parallelly sided piece, situated at the interior margin, contiguous to the scutellum, and, in repose, partially passing its sharp edge beneath it ; close to this, upon the exterior, lies the HEM- ELYTRUM (PL XV. f. 1, 6), which is the largest of all the divisions, and forms a triangular horny piece, which enters the mesothorax with its anterior acute angle. The APPENDIX (PI. XV. f. 1. c), which is frequently wanting, follows the HEMELYTRUM; it is likewise a trian- gular, but much smaller, and often right angular horny plate, the right angle of which is contiguous to the exterior margin of the hem- elytra, so that the hypothenuse is turned towards the inner margin. The fourth and last division is attached to this, and which is called the MEMBRANE (membrana, PI. XV. f. 1. d), from its membranous quality. It is generally of a rhomboidal form, with obtuse angles, or it is ovate, but more rarely forming a somewhat reversed half moon. It likewise consists, like all wings and wing-cases, of a superior and inferior layer, between which horny ribs pass, and distend it. The pergamentaceous cases, called TEGMINA, differ from the true elytra, by being less firm in their substance, and from the true wings, by their greater strength. They are situated at the same place with the elytra and hemelytra, and they approach nearer to the latter in their structure, but most closely to the true membranous wing. For, although in the hemelytra the ribs and veins are more apparent, yet in the tegmina they are so clearly developed, that they are no longer subject to doubt. Lower, in the anatomy, we shall find that the elytra also possess such veins, but which, from the thickness of their substance, do not become prominent. In form, the tegmina are subject to greater differences than the THE THORAX. 9f> elytra or hemelytra ; for sometimes they are shorter than the body, broad, ovate (Gryllotalpa) ; sometimes as long, with parallel sides, rounded (Blatta) ; sometimes longer, very slender, acute, and narrowed at the base ( Gryllus, Fabr.) ; and sometimes very wide, large, and ellip- tical (Mantis'). By means of the veins originating from a main stem, which furcate from the very base, they are divided into three prin- cipal areas; the first of which, seated upon the exterior margin (PI. XV. f. 2, A), is in general the narrowest, and towards the apex of the tegmina contracts gradually to a point ; it is also usually of a harder substance than the following. This second piece (PI. XV. f. 2, B) lies contiguous to the former, and is separated from it by the before- mentioned chief vein ; it is the largest of the three areas, embraces the majority of the ramifications of the veins, becomes gradually wider towards the apex of the wing, and consists of a softer membrane than the marginal area. The third, or sutural area (PI. XV. f. 2, c), lies inwardly beyond the second, and it is also harder than the central area ; in many families it forms the superior dorsal covering, while the two other areas fall down upon the sides of the body (Gryllodea, Locusturia) . It varies considerably in figure ; it, like the marginal area, is sometimes a very pointed isosceles triangle (Gryllodca); sometimes, as in the hem- elytra, a space surrounding the scutellum (Achetaria) ; it also some- times appears to be wanting, or not distinctly separated from the cen- tral area (Mantodea). There seems likewise to be some difference in the ramification of the horny veins throughout these three areas ; in the marginal one they are small, broad, multitudinously divided veins, which appear to spread from two or three radiating main branches. In the central area, the large stems spread more parallelly from the inner side of the chief stem, which separates them ; the transverse veins also run parallel, and thus divide the whole area into small squares. In the inner area, lastly, the veins are most delicate, and ramify variously on all sides, whereby an irregular reticulation is formed. 80. The mere membranous wings (/) distinctly differ from the pre- ceding organs by their transparency, and purely membranous nature. In respect to their situation and general function, they perfectly agree with the former ; but the wings are exclusively organs of flight, while 96 PARTIAL ORISMOLOGY. the different kinds of elytra have the additional purpose of covering the soft upper part of the abdomen. Therefore all insects provided with wings only are entirely inclosed in a hard case, and., although they possess wings, are equally unprovided with a protection against exterior influences, as those genera and species which have no wings. The observations we are about to make upon the wings will refer to their exterior perceptible construction, and their different forms and clothing. The investigation into their progressive conformation, their internal coherence, their functions, &c., belong to other divisions, and will be treated upon in the proper place. In outward appearance, the wings present themselves as flexible, but firm, dry membranes, which are traversed by various horny ribs. These RIBS (costce}, or more properly VEINS (nervae), as they are, in fact, vessels, but incorrectly called NERVES (nerod), arise all from the roots of the wing, and through their main branches, of which we usually observe two or three, they are connected with the thorax by articulation. The first and most exterior of these veins is called the MARGINAL RIB (costa marginalis, PI. XV. a, a), or, by pre-eminence, the RIB (cosla), which forms its anterior margin when expanded, and extends from the base to the apex. Jurine, who made use of particular names to indi- cate the veins of the wings of the Hymenoptera, calls it radius ; and a horny expansion of it in its course, which is particularly distinct in this order, but which is also observable in others, he calls the POINT of the wing (punctum, or carpus) ; but Latreille, and Kirby and Spence call it STIGMA (PI. XV. f. 4, /3). The second vein originates close to the first, and distinguishes itself from the rest, like the former, by its superior robustness. Its course also is in a direct line towards the apex, but it gradually diverges from the marginal vein ; so that the portion of the wing enclosed by it, takes the form of a triangle. Kirby and Spence call this the posfcosta (PL XV. f. b, b, b) ; Jurine, cubitus ; and Latreille, itcrviif. internus. It also ultimately attains the apex of the wing. It is seldom simple ; in the majority of cases it divides itself into branches, so that the main stem ceases before it attains the disc of the wins; ; but O ' the branches extend from the separation, either continuing simply to the end of the wing, or again ramifying. By means of these ramifica- tions, a varied net-work is produced upon the disc of the wing, the reticulations of which are tolerably constant in the several orders, families and genera, and is therefore of importance for the determina- tion and distinction of the groups. The spaces enclosed by these veins THE THORAX. 97 are called AREOLETS (areolte), or CELLS (cellules, Jurine) ; and those lying close to the marginal rib are called MARGINAL AREOLETS (areolee marginales, PL XV. d, d) ; Jurine's, cellulce radiales ; those succeeding to them, and formed by the postcosta and its branches, SUBMARGINAL AREOLETS (ctreoltB submarginales, PL XV. e, e) ; cellulce cubitales of Jurine. The transverse veins which branch from the longitudinal nervures of the main stems, are called the CONNECTING VEINS (venae anastomosis), or nervi recurrentes of Jurine. The areolets seated at the end of the wing, and, sometimes not quite closed, are called IMPERFECT (areolce imperfects, PL XV. J\ f), or cellules incom- pletce of Jurine. The APPENDED CELL (cellula appendicea) of the same author is a small, almost triangular areolet, situated at the apex of the wing, which is formed by the furcate division of the vein spring- ing from the stigma (in many genera of the Tent.hrcdonodea ; for example, Perga, &c.). The space behind the second principal vein of the wing is its third and last chief areolet, Avhich, in many cases (Hymenopterd), is ante- riorly limited by a peculiar, slight vein, originating near the second principal one ; and this areolet extends to about the middle of the margin of the posterior wing. Several other veins and areolets (nervi et cellula; brachiales, Jurine) are found within this space, which, as they do not vary much in large groups, are consequently of less importance for the determination of genera. In the membranous wings we also rind the same distribution into three chief areolets which we have already indicated in the tegmina, and we here distinguish them, with Kirby, as the MARGINAL AREOLET (area costalis sive marginalis), CENTRAL AREOLET (area discoidalis s. intermedia), and POSTERIOR AREOLET (area analis s. posterior). In repose, during which the wings lie parallely upon the body, the poste- rior areolet passes beneath the central one, turning upon its limitary vein, like a door upon its hinge. In those orders, however, in which we meet with elytra, or an analogous structure, the inferior wings are folded in several directions. Thus, in the beetles, the whole apex of the wing is very generally folded from the stigma back towards the base, or the whole wing, from this point, folds itself like a fan (Forficiihi) , or this plication originates from the base of the wing, according to the direction of the radiating veins (Orthoptera}. The preceding general description treats chiefly of the anterior wings; H 98 PARTIAL ORISMOLOGY. but it will equally apply to the posterior ones, when they are of the same size and quality as the former (see the table, 79). Where the poste- rior wings differ in form from the anterior, they are in general smaller often, however, broader, if not longer. It is chiefly in the Orthoptera that we observe this more significant size of the posterior wings ; in these they are sometimes even longer than the anterior, and extend beyond them ( Gryllotalpa) ; it is the same in some beetles with short elytra (Necydalis, Atractocerus) . In general, however, the true wings of an Order are perfectly uniform in structure, although their veins ramify differently, and, this also applies more generally to the pos- terior wings, which less distinctly show the above-described separation into three principal areolets, although, upon a careful inspection, these would not be found deficient in them. The following are the most important orismological definitions of the wings :- The ANTERIOR WINGS (alee anteriores) are those attached to the second thoracic segment; they are also called SUPERIOR (al. supe- r lores) from their covering the posterior ones in repose ; or, the FIRST (primaries) from their preceding the others in flight. The posterior wings have had, from opposite reasons.- opposite names applied to them, as al. posteriores, al. inferiores, and al. secundarice. In each wing we distinguish, as the ANTERIOR MARGIN (margo anterior], or EXTERIOR MARGIN (margo externus), that margin which, in flight, lies in the direction of the head; that opposed to it as the INNER MARGIN (m. internus) ; the third, generally taking the direction of an obtuse angle, with regard to its situation as to the others, is called the POSTERIOR MARGIN (m. posterior}. The angles formed by these margins at their point of contact, receive the following names : the ANTERIOR ANGLE (angulus anterior} is that at the apex of the wing, formed by the ante- rior and posterior margins ; the POSTERIOR ANGLE is that formed by the contact of the posterior and interior margins. We have already made mention of the humeral and scutellar angles. The general outline of the wings is distinguished according to its form; the following terms are used to express them: FALCATE (falcatcB, PL XV. f. 12) are wings whose anterior margin forms a circle bending outwards, and their posterior margin is also directed forwards (many Lepidopterd). TAILED (eaudatce, PI. XV.' f. 13) are those which have a long and THE THORAX. 99 narrow appendage extending from the internal margin. This form is found chiefly in the posterior wings of the butterflies (Pap. Machaon, Podalirius, &c.). DIGITATE (digitata, PI. XV. f. 14) is a wing, which has its other- wise undivided surface indented with deep incisions between the ribs or veins (Orneodes). Besides these outlines, which are peculiar to the wings, we likewise find in them the majority of the differences mentioned in 18. The same applies to the differences of margin ; we therefore refer to 20. The surface of the true wings is subjected to but few changes ; in general it is a smooth skin, with here and there some hair spread over it (in many Diptera, for example, Psychoda}. In one order, however, (the Lepidoptera) , the general law prevails for their being clothed with flattened scales (alee squamosas). The situation of the wings in repose is much more various in pecu- liarities. We proceed to the consideration of these differences, and thereby form a conclusion to the investigation we have here made upon these organs. EVEN (alee planet), are those wings which, in a state of repose, preserve the same extension as when in motion. Opposed to them are the FOLDED wings (plicatce). By this term we understand such as are longitudinally folded in repose, like a fan, and expand only during flight into a uniform surface (Orthoptera) . We consider such wings as RE-FOLDED (replicatce) , when their apex falls back upon the base. CONVOLUTED wings (al. convolutce] , are such which embrace the body from above downwards, and enclose it as in a tube (Crambus). INCUMBENT (incumbentes), when, lying parallely upon each other, they cover the abdomen above (Tenthredo). CROSSED (cruciaice), are those incumbent wings which pass over each other only at their apex (many Bees, the hemelytra of the Hemi- ptera heteroptera). HORIZONTAL (horizontales}, whose direction is in the same plane with that of the body. The reverse of these are the ERECT wings (erectce), whose line of direction is perpendicular to the plane of the body (Papilio). EXTENDED (extensce), form also in their direction a right angle with the body, but lie in the same plane with it ; from these we must dis- H 2 100 PARTIAL ORISMOLOGY. tinguish the OPEN wings (patentee) by the angle which they form with the axis of the body? being at least of 45 ( Tabanus, Musca, &c.). The ERECT-OPEN wings (erectee patentes) do not lie in the same plane with the body, but cut it at an angle of less than 45 (some Lepidoptera, for example, Hesperia). CONNIVENT (conniventes), are such wings which, in repose, perfectly unite with each other at their corresponding margins (Papilio] ; DIVARICATED (divaricate), are such which only partially cover each other (Agrion). DEFLEXED (defle.vai), are such which, with their internal margin, meet at an acute angle, and so cover the body (many Noctuce) from them must be distinguished the REVERSED wings (reverses') by this, that the anterior margin of the posterior wing projects bevond the same part of the anterior wing (Gastrophaga alnifolia) ; this is also often the case in the open wings. B. THE LEGS. 81. The other chief organs of motion, the LEGS (pecles), are distinguished from the wings in a multitude of ways, in form and number, as well as in their function. In number, they exceed that of the wings by one-half; for although we never observe more than four wings, we constantly find, in perfect insects, six legs. These six legs are placed in pairs upon the lower part of each of the three segments of the thorax, and consist of many joints, to the observation of which we now pass. We have already become acquainted with the ACETABULA (ace- tabula') upon the segments or plates of the breast, for the reception of the legs. I. These cavities receive pieces formed exactly to their dimensions, frequently conical, or more longitudinal and rounded, called the HIPS (coxae, PL XVI. f. 1, ). Surrounded and enclosed by a corneous substance, it has, only at each of its opposed ends, an opening for the passage of the muscles which unite it to the surrounding parts. This typical form of structure is somewhat modified by the closer or looser union of the coxae with the thorax ; so that it appears sometimes as a cone truncated at its apex, and then attached to the thorax by the whole of its basal surface (Diptera, Lepidoptera, Hymenoptera, &c.); and sometimes moves itself freely in a proportionate cavity of the THE THORAX. 101 thorax, to which it is affixed by a single small spot (many Coleoptera) ; and sometimes, lastly, it displays itself more flattened, in which case it is affixed to the thorax by a firmer and closer union, which admits of no free motion (for example, the posterior coxae of Dyticus, llu- prestis, &c.). In this last case, frequently also in the first, the coxae appear to belong more strictly to the thorax than to the legs, as they stand in much more intimate connection with the former than with the latter ; but their very general free motion speaks strongly against the adoption of this opinion. II. A much smaller corneous piece, the TROCHANTER (PI. XVI. f. 1, 6), stands in moveable connection with the coxa. The form of this part is subject to many changes ; we sometimes rind it quite annular, with surrounding, equally high sides ; sometimes compressed and obliquely truncated, or prolonged into a lateral point (Carabus, Dyticus}. This form is found chiefly among the beetles; in other orders (the Diptera, for example) it has very generally the annular form. In these orders, the articulation of the coxae consists only of a firm membrane ; but in the former, ball-joints appear to be fitted to corresponding sockets, whereby the strength of the union is very much increased. III. The trochanter is succeeded by the THIGH (femur, PI. XVI. f. 1, c), which is the largest joint of the leg. It is generally of a cylin- drical, but not always equally thick, frequently knobby or clavate, form. It is very often much longer than the two first joints toge- ther; in general also longer than the following, but always thicker and more robust. Besides this roundish form, we also observe angular, pris- matic, parallelopipedal, flat, very much compressed, and provided with a longitudinal furrow, or even globose and elliptical forms. Its union with the trochanter is sometimes very close, at others looser. We meet with its firm conjunction in the Coleoptera. In these the motion of the thigh appears to be very limited, and in general the trochanter moves in the articulation upon the coxae, when the thigh is touched ; it is different in the Diptera, in which the freer union of both admits of greater motion. The upper surface of the thigh is like that of the coxa and trochanter, generally smooth ; but its margins are not rarely armed, sometimes with solitary spines, sometimes with hair, or with long cilia. Some have broad lobate appendages ( Trachusa lobata, Mantis oratorio). We do not usually observe such processes upon the two first joints, for coxa? armed with a spine belong to the rarer exceptions ; these we 102 PARTIAL ORISMOLOGY. observe among some of the Ichneumons (Icli. melanogonus, Grav. ; Pimpla mesocentra, Grav.) IV. The fourth joint of the leg is the SHIN (tibia, PI. XVI. f. 1, rf.) But in the same way as the thigh is united to the hip through the medium of the trochanter, so is the shin connected with the thigh, viz. by ginglymus, but in a reversed direction, for whilst in the former articu- lation the shanks are directed upwards, in the latter it is the apex. With respect to its form, it is very generally as long as the thigh, and it is equally often thinner and more slightly framed. Notwithstanding which, we observe more differences in the tibia than in the thigh ; it is found conical, tubular, triangular, quadrangular, compressed either partially or entirely, leaf-shaped, uneven and rough. It is not unfre- quently that we perceive them armed or clothed with spines, either solitary or placed in rows, with very long hair, teeth, fringe (tib. Jimbriatce), and setae. Indeed they occur more frequently upon the shank than upon the thigh. In form, however, it is very much regulated by that of the thigh, and its structure appears to agree as intimately as is compatible with the preformed figure of that joint. For example, should the thigh be conical, the shank forms a bow, which fits closely to the cone (Chalets'), or if the thigh be convex, the shank then forms a corresponding inflection. The same is the case in raptorious legs (Mantis). At the end of the shin, and around the cavities, wherein the following joint articulates, in general we observe some spines, which are usually called SPURS or TERMINAL SPINES (Calcaria, Spicula, PL XVI. f. 1. 8, 8.) They are indeed most fre- quently mere processes of the horny substance, but they are sometimes articulated, and have a free motion at the will of the insect (Mantis'). In this case they form a species of pincers (Hylobius Abietis), which assists the insect in climbing. V. It is to the shin that the last division of the leg, the FOOT (tarsus, PI. XVI. f. 1, d, f/). It possesses, besides, two lateral VALVES (valvulee, the same, f. 6, a, a), between which the sting lies like a sword in its case. If the sting project beyond the abdomen, they accompany it, but only in those insects in which it lies freely exserted. In the bees and wasps, which use it also as an offensive weapon, the valves remain within the abdomen during its use. Latreille calls the freely projecting ovipositor the BORER (terebru). 2. The TUBE (tubulus, PI. XXIV. f. 15) is a mere continuation of the abdomen, which occurs in Chrysis and many Diptera, viz. the house-fly. It consists of several cylindrical joints, which are united by a soft membrane, and are retractile within each other, like the joints of a telescope. This kind of ovipositor is found only in insects which have but few abdominal segments, whence it is not improbable that the joints of the tube are nothing else than segments of the abdomen itself. 3. The SHEATH (vagina, PI. XXIV. f. 10 ) consist of two long, convex continuations of the abdomen, generally inclining upwards, which, when * Meigen. Zwcif., Vol. iv. PI. XXXVI. f. 21 THE ABDOMEN. 113 placed together, exactly correspond, and form a single organ the ovipositor. Between them lies the female sexual aperture, and the eggs are laid encompassed by them. (Locusta.} Besides the above-named organs, several other forms are observed at the apex of the abdomen, which neither belong to the anus, nor can be considered as standing in connection with the sexual organs. They bear the general name of TAIL (cauda) or CAUDAL, APPENDAGES (Appendices caudales) : as such we may consider The FORCEPS (forcipes, PI. XIV. f. 8), two toothed cheliform hooks, which move in opposition to each other, in the earwig. (Forficula.} The FORK (furca, PI. XIV. f. 9) a continuation of the lower portion of the terminal segment, which is directed forwards, and is furcate, by means of which the insect springs upwards. (Podura, Smynthtirux.') The STYLES (styli, PI. XIV. f. 10), two short exarticulate processes, close to the anus in Staphylinus. The CERCI (cerci, PI. XIV. f. 11), likewise short, lanceolate, and generally flattened and articulate appendages at the sides of the anus. (Blatta.) The THREADS (fla, PI. XIV. f. 12), longer or shorter articulate cylindrical processes of the last segment, which grow gradually thinner. (Acheta, Ephemera, Lepisma.) The BRISTLES (setts, PI. XIV. f. 13) are such appendages when exarticulate and simple. (Mackilis.) The SIPHONETS (siphunculi, PI. XIV. f. 14) are the hollow processes upon the upper side of the penultimate segment in the plant-lice (Aphis), whence the sweet juice exudes which the ants seek so eagerly. SECOND SECTION. ANATOMY. 86. THE examination of the exterior form of the body is succeeded by the investigation of its internal construction. This branch of natural science o is distinguished by the name of ANATOMY (derived from avare/jiVEiv, to cut up) ; but the portion of it which treats of the interior structure of insects might be appropriately called Entomotomy (derived from IVTO- p.ov, insect, and ripvtiv, to cut). As it was not our object in the preceding chapter to explain the mode whereby the different parts of the body stand mutually con- nected, but which combination and connection is of importance to the formation of the complex organism we have already examined exter- nally, it is therefore incumbent upon us, in this section, to display the fundamental parts, or, as it were, the keys of this entire organism, and what the different materials are which must necessarily unite to con- stitute the organic body we have just treated of. The information which will be conveyed in this section will consequently be richer in its results towards a knowledge of the life of insects in general, as it will materially tend to show how far the differences of form are influ- enced by differences of structure, and what their mutual relations are. We shall nevertheless restrict ourselves, even in this section, to a mere description of forms, but principally of the internal parts, and conse- quently of their structure, reserving the reply to all questions upon the importance of each individual organ, its function, and sphere of action, to the next ensuing section. But, before we pass on to the contemplation of these new objects, a few general remarks will not be inapposite to determine the natural succession of the investigations we are about to institute. ANATOMY. 115 87. Experience has instructed us that every organism is not only tran- sitory in its duration, but that it also requires the assimilation of fresh matter, if it is to be preserved from perishing immediately after its appearance. To meet this necessity nature has furnished every organic body with two different sets of organs, which are called systems, the one of which provides for the preservation of the individual by means of nutriment, and is thence called the NUTRIMENTAL SYSTEM, and the other for the continuance of its resemblance, or kind, and which is called the RE- PRODUCTIVE SYSTEM. Both systems, therefore, are the essential peculiarity of every organic body, and without them no organism can be imagined. 88. Indeed, the very lowest organic bodies, plants, display no other organs than such as belong to these two systems; but the animal destined to a higher grade of organisation adds to the phenomena of vegetable life two new proofs of its vitality, and which must be treated as the results of a greater freedom of nature. This liberty displays itself at once in its independence of its original place of abode, by the power it possesses of constantly changing it; in fact, the power of LOCOMOTION is the first and principal peculiarity of the animal, and this power also qualifies the second phenomenon peculiar to animal life. If, namely, the animal is to make an advantageous use of the freedom it derives from its power of locomotion, and if it be to be secured against all the disadvantages consequent upon this power, it must necessarily possess faculties which apprise it of the nature of its situa- tion, and these it has received in the organs of SENSATION. Both, consequently, the organs of locomotion and sensation, are peculiar to the animal, and wholly wanting to the plant, whilst the organs of nutriment and re-production are common to both. 89. And as the organs of nutriment and re-production are first observed in the plant, and as the whole vegetable kingdom displays no higher development of life, they are distinguished as VEGETATIVE ORGANS, and their circle of action the VEGETATIVE SPHERE. Whereas the organs of locomotion and sensation, as the exclusive peculiarities of the animal, i2 116 ANATOMY. have received the name of ANIMAL ORGANS, and their compass of action the ANIMAL SPHERE. 90. The greater development or separation into several distinct organs, and the more complex structure of each, are the phenomena gradually displayed in the progressive ennoblement of the animal kingdom, com- mencing at the most simple conditions of animal existence. Insects maintain in every respect a central situation in this series ; their organs, therefore, will not display to us a very artificial structure, nor will their combination be very complex. But we shall find the above indicated four chief differences, which are dependent upon the vital phenomena of the organism, sufficiently distinctly exhibited in them. Now, as the several organs of each individual system not only aim at one object in their functions, but also display considerable conformity in their structure, it will be suitable to regulate the arrangement of our present investigation by their differences, whence we derive the follow- ing themes : I." Investigation of the vegetative system and its organs. These are, A. The organs of nutriment, consisting of The general integument. As this in insects is a horny case, to which the organs of locomotion are attached, its description must be classed with the consideration of the animal organs, it being but the passive agent of motion. Therefore of a. The INTESTINAL CANAL with its appendages, as digestive organs ; b. The HEART and BLOOD VESSELS, as organs of circulation ; c. The AIR VESSELS, as respiratory organs. B. The organs of re-production ; consisting of a. The FEMALE organs of re-production, and b. The MALE organs. II. Investigation of the animal system and its organs. A. Organs of locomotion : a. Passive organs of motion ; here the EXTERIOR INTEGUMENT as analogous to the osseous system. b. Active organs, the MUSCLES. B. Organs of sensation: a. The BRAIN; b. The NERVOUS SYSTEM in general ; VEGETATIVE ORGANS. 117 c. The NERVOUS SYSTEM OF THE DIGESTIVE ORGANS ; d. The ORGANS OF THE SENSES. We consequently commence our description with the vegetative organs, as being the inferior ; and thence proceed to the survey of the animal organs, as the superior ones. But we do not wish by this arrangement to imply that the lowest insects have no organs of locomo- tion and sensation, but that in them both these organs, and also par- tially the vegetative ones, are not quite so perfectly developed and completely combined as in the higher orders, and from the circumstance of this difference the latter stand HIGHER and the former LOWER in the system. And by these expressions, as well as by the synonymous ones, of MORE or LESS PERFECT, we would indicate that the structure of the former is more complex, artificial, and various than the groups characterised as standing lower and less perfect. But each group is perfect in its kind. FIRST SUBSECTION. VEGETATIVE ORGANS. 91. THE organs of the vegetative sphere are, as it were, transmitted from the plant to the animal ; it will therefore be not unimportant if we can prove that their fundamental texture displays a vegetable origin. The plant commences its existence in the form of a cell ; cell is added to cell, and the entire vegetable is but a congeries of small cells, with here and there long delicate tubes interspersed, forming, as it were, free passages between them. All the organs of vegetables consist of these two forms, consequently the nutrimental and re-productive organs must display a similar, or at least an analogous, structure, if they are to prove themselves of vegetable origin. Nothing, in fact, is more astonishing than the confirmation of this law ; for cells, which in animals become small vesicles or larger bladders, and tubes, constitute the various forms of the vegetative organs. A vesicle, the egg, is the 1 1 8 ANATOMY. origin of animal existence ; vesicles distend themselves, and become cases ; they link themselves in a series, and form vessels ; and thus, by degrees, each vegetative organ is formed from the vegetable original. We will examine this more closely in the individual organs. 92. The INTESTINAL CANAL is a tube which originated from the elonga- tion of one or the connection of several bladders. This is proved not only by its form in the lower animals, but also from its being in many, likewise in the larva? of insects, a mere blind sack, consequently a bladder open only in front. In animals of a higher grade, in which it consists of several divisions separated by constrictions, it is very easily imagined as consisting of the union of several bladders. The same holds good of the vessels : for example, the chief vessel of insects, namely, the large dorsal vessel, so evidently displays a cellular construction that we may not consistently doubt its original growth from bladders. The very name of the air-tubes announces their form. It must, how- ever, strike as important that the air-vessels of insects have so deceptive a resemblance to those of plants that everybody mxist immediately admit of their analogous structure. The vegetable origin of the nutrimental organs is thus evidently proved. 93. It is not more difficult to show the same in the organs of reproduc- tion. These, namely, very much more distinctly display their vesicular origin. The OVARY of the female is a large bladder, containing many smaller ones, the eggs. The OVIDUCT is an elongation of this large bladder ; the UTERUS is another distension of it, and the VAGINA ano- ther elongation : other incidental appendages of the above parts display more or less distinctly a vesicular form. It is the same in the male organs. The testes have not uncommonly the shape of a bladder (Lamellicornid), or else they are long convoluted tubes, which we know to be but modifications of bladders ; the VASA DEFERENTIA are elongations of these bladders; the VESICA SEMINALIS another distension of it, and the DUCTUS EJACULATORIUS another and its final constriction. Thus the sexual organs are a still more evident repetition of the ve&icular form, they being always closed at one end at least. THK ORGANS OP NUTRITION. 119 94. We shall show in full detail, at its proper place, that the character of the organs of the animal sphere differs wholly from the vesicular character of the vegetative organs by the integral solidity of each indi- vidual part. FIRST CHAPTER. OF THE ORGANS OF NUTRITION. 1. THE INTESTINAL CANAL AND ITS APPENDAGES. 95. The intestinal canal (tractus intestinorum) is the internal tube, extending from the MOUTH, appropriated to the reception and trans- formation of the nutriment. It has in general a second aperture opposed to the first, the ANUS, through which the indigestible unassiuiilating remains of the food are rejected. The instances in which such an anal aperture is deficient are very rare among insects, and occur only among larvae and maggots, but never in the imago. This tubular structure of the intestinal canal is subject to con- siderable modification from distension and constriction, by means of which it is separated into several divisions, which have very justly received different names, from their functions being dissimilar. Be- sides these separations of the intestinal canal itself, we observe peculiar processes and appendages, which originate from it, or which, as perfectly independent parts, merely open into it. Their variety and modifications produce relations which yield multifarious differences in form and structure, and which link certain groups of insects more closely together by their complete uniformity, whereas they separate others, in which such a similarity of arrangement is not observed, more distinctly from each other, and thus more fully corro- borate the dissimilitude expressed in their exterior conformation by this difference of their internal structure. 120 ANATOMY. 96. The entire intestinal canal consists of three skins, or layers of mem- brane. The innermost membrane (PL XVII. f. 1), which may be considered as a continuation of the exterior epidermis, is very smooth and texture- less, and only sometimes longitudinally folded, and armed above with horny lines, ridges, or teeth (PI. XVII. f. 2. 5 7)- It is particularly distinct in the pharynx, crop, and proventriculus, the horny teeth of the latter being formed by it. This internal membrane is most apparent in insects with hard cases, as the Coleoptera and Orthoptera, whereas it is not so evident in the haustellate Diptera and Lepidoplera. From the proventriculus it forms a very delicate perfectly uniform covering, and generally occupies less compass than the other intestinal mem- branes. We here call it the epidermis, it being its analogue, or pro- perly, the mucous membrane, as it corresponds with the tunica mucosa of the superior animals. The second layer, which we call with Straus the PROPER skin (inem- brana propria), is white and smooth, and usually thin, but sometimes thicker and spongy, most frequently without any texture, but occa- sionally figured (Hydrophilus, PI. XVII. f. 2.). This membrane, which Ramdohr treats as a layer formed of transuded chyle, is pecu- liar to the intestinal canal, and is not found in the other internal organs ; it may therefore be considered as a continuation of the second layer of the exterior integument, of which we shall treat below. Indeed, the space between the mucous membrane and this peculiar skin, which is very considerable in the stomach, and particularly in caterpillars, is often occupied by a flocky web, formed of transuded chyme, and this may have misled Ramdohr in his idea of it. According to Straus, horny prominences are sometimes observed in this intermediate skin, parti- cularly in the vicinity of the stomach, which might be considered as absorbing pores, but which Straus, perhaps more correctly, treats as glands, and they are therefore called gastral glands (glandules gastric fe^). I have observed these organs only upon the inner surface of the mus- cular membrane, but particularly distinct in Hydrophilus, in which insect the long cylindrical stomach is completely and regularly covered with such glands, which consist of a transparent case inclosing a darker kernel (PI. XVII. f. 3.). The third layer (PI. XVII. f. 3 and 4.) is a compact, firm, fleshy THE ORGANS OF NUTRITION. 121 muscular membrane (tunica muscularis), in which distinct longitudinal and transverse vessels can be discerned, and it lies closely upon the preceding. These vessels, which are sometimes completely reticulated, sometimes furcate separately and rejoin in the same manner *, are gene- rally of a uniform size, but occasionally the transverse ones are stouter, the others more delicate and slender, but also more numerous and closer together, so much so that their distinct threads may be consi- dered as the separated bundles of muscles t. This muscular membrane is not equally observable in all parts of the intestinal canal : it is very obvious in the pharynx, stomach, and colon ; but it vanishes almost entirely in the crop or craw. 97. The situation of the intestinal canal is the same in all insects. It always commences as a cylindrical, and chiefly narrow tube at the somewhat wider cavity of the mouth, and proceeds in a direct line through the head and thorax. It takes the same direction in all insects which have a long and at the same time thin body (e- g. Pimpla, Tipula, Agrion). In these cases, however, the intestinal canal is of the same length as the body, and only in some of the broad- bellied ones, for example, the long bugs (Gerris, Emesa, Ranatrci), it makes a small curve before its termination, so that it becomes about half as long again as the body. But if the creature be thick bodied, and the cavity of the abdomen is distended on all sides, the intes- tinal canal becomes longer than the body, and makes convolutions within the cavity of the abdomen ; but it always passes in a direct line through the head and thorax. These convolutions of the intestinal canal are kept in their proper situation by the multitudinous branches of the air-vessels which spread about them; indeed, this reticulation of the air-vessels is so delicate and firm that it not only makes it difficult to represent the intestinal canal with all its appendages (which besides is closely enveloped in the fatty mass) in its full extension, but makes a perfect separation of all these air-vessels absolutely impossible. We never find in insects a peri- toneum, which in the higher animals retains the intestines in their place, but its purpose is supplied by these air-vessels. * Ramdohr, Ueber die Verdanungswerkzeuge der Insecten Halle, 1811. PI. XIV. f. 4, from Pompilus Viaticus. f The same PL XVII. f. 2., from the fauces of the larva of the Ant-lion. ]22 ANATOMY 98. The length of the intestinal canal increases with its convolutions ; or these rather are but the consequences of its extension. We very fre- quently find the intestinal canal twice the length of the body ; indeed so often is this the case that it may be considered as the most usual struc- ture. A nutrimental canal of this extent is called MODERATELY long; such an intestine makes from one to three convolutions, according to their size. The LONG intestine (Chrysomela, Cimcx) makes also two or three, but larger convolutions, and is from three to five times the length of the body. The intestine is, lastly, very long in the Lamelli- cornia, in which it is from seven to eight times as long as the body, and makes many folds in the cavity of the abdomen. But these proportions refer only to the perfect insect, for the majority of larvae, namely those with a perfect metamorphosis, have a nutri- mental canal of the same length, or at most of twice the length of the body. This short intestine increases in length in every distinct period of its life ; but some instances occur in which this gut becomes shorter during the metamorphoses, namely, in the Diptera, the larvae of which have a very long and much convoluted intestine *. 99. No general law regulating the various length of the intestinal canal has yet been discovered ; in insects, in particular, it appears exposed to much irregularity. It is not however improbable, from all hitherto instituted investigations, that herbivorous insects have a longer and more distended intestine, and that those which feed upon animal matter have it shorter and narrower. We, however, find a decided exception in the vegetable devouring Orthoptera (e. g. Gryllus, Lo- custa), their intestine being not much longer than their body, but at the same time very broad. We perceive greater uniformity, if not in length yet in structure, in the different orders of insects, and this law we shall observe to prevail still more forcibly in the still smaller groups. 100. We will now pass from this general description of the entire intes- tinal canal to the examination of its different divisions. We can there- * Ranidohr, PI. XIX. f. 1 and 2. THE ORGANS OF NUTRITION. 123 fore make a primary separation of it into its SEVERAL DIVISIONS and its APPENDAGES. The divisions of the intestinal canal are, the PHARYNX, the (ESO- PHAGUS, the CRAW, the PROVENTRICULUS, the STOMACH or VENTRI- CULUS, the DUODENUM, the ILIUM, the CCECUM, and the COLON. The peculiar appendages of the intestinal canal are, the SALIVARY, BILIARY, and ANAL VESSELS. These parts are never all present together ; sometimes one is wanting, and sometimes the other. For example : insects with a suctorial mouth never possess apparent pharynx, but the oesophagus originates imme- diately at the base of the sucking tube ; they also want the proven- triculus, instead of which they possess a bladdered crop, which how- ever does not occur in mandibulated insects. The part most frequently deficient is the duodenum, which has hitherto been observed only in some of the pentamerous Coleoptera, after which the ccecum is least frequently present, for it appears to be peculiar to those families only the genera of which feed upon animal matter. With respect to the appendages, the biliary vessels are seldom want- ing (Chermes, Aphis}, the salivary ones frequently, but the anal vessels very generally. THE PHARYNX. 101. The pharynx is the distended commencement of the oesophagus, bordering upon the cavity of the mouth, and is found, as we have recently remarked, only in the mandibulata, consequently in the Cole- optera, Orthoptera, Neuroptcra, and Hymenoptera. In these it is nothing else than the almost trumpet-shaped commencement of the oesophagus, and in the majority of cases is not separated from it by any evident difference of texture or construction. In some of the grass- hoppers and cockroaches, in which, in consequence of their large man- dibles, the cavity ' t of their mouth is very expansive, their pharynx is very much distended, and more clearly separated from the much narrower oesophagus *. Its membrane is more dense and compact than that of the latter, excepting which it displays no other difference. The mucous and muscular membranes lie close together, and it is scarcely possible to * Ramdola, ib. PI. I. f. ( J. 124 ANATOMY. distinguish the proper membrane between them as a separate layer. A free space is naturally not found, as in the stomach. THE (ESOPHAGUS. 102. The oesophagus (PI. XVII. 22, A, A,) extends from the pharynx to the stomach ; it is distinguished from the former by its smaller capacity, and from the latter by a variation in structure. The most remarkable form of the oesophagus is doubtlessly its very general furcate division in the Lepidoptera, and that from each of the two spiral sucking tubes it originates by a distinct branch, which branches then unite into one channel. In general the branches of the fork are very short, but in the swallow-tail butterfly (Pieris Machaon, O.) their union into one tube commences only at the thorax *. In the other orders of insects the oesophagus passes through the entire cavity of the thorax as a simple tube, and either terminates where the cavity of the abdomen commences, or before this, within the thorax itself; for example, in its centre in those insects the cavity of whose thorax is broad, and which consequently admits of a greater expansion of the organs which traverse it. The length of the oesophagus therefore depends upon the length and dimensions of the thorax. Insects with a thin and narrow, and in particular with a petiolated abdomen, have a long oesophagus, when the thorax also is long (Pimpla, Fcemts) ; and it is the longer in proportion to the entire intestinal canal, the shorter, narrower, and smaller we find the abdomen. The most remarkable proportions must occur in this respect in the genus Evania, but which has never yet been anatomically investigated. The longest oesophagus yet observed consisted of more than half of the entire intestinal canal f ; and among the shortest is that of the cockchafer, which occupies scarcely one-sixtieth of the entire length of that canal J. We are already acquainted with the texture of the oesophagus ; its central layer however is very slight, whence the two other membranes lie closer together, which, as Ramdohr assures us, makes their separation very difficult. The inner membrane is generally here quite uniform, much more rarely thicker in parts, almost like parchment, or, as in Carabus, * See Treviranus, Vermischte Schriftcn, vol. ii. p. 200. f In Pimpla Enervator and Pompilus viaticus, Ramdohr, PI. III. f. 2 and 3. t Ramdohr, PI. III. f. 1. THE ORGANS OF NUTRITION. 125 Meloe, Chrysomda, Blatta, and the grasshoppers (PI. XXI. f. 2 and 3), internally covered with short stiff setae and teeth ; the muscular fibres of the exterior membrane generally lie regularly above each other, but they sometimes form a loose confused net-work from open spaces remaining here and there between them. The separation of the oesophagus from the stomach is effected some- times by a positive constriction (Diptera, PI. XVIII. f. 3.) ; it occa- sionally passes insensibly into it, and sometimes the crop intervenes between them, as the organ of transition ; in this case the oesophagus expands by degrees into a sack-shaped CROP (ingluvies, PI. XVIII. f. 1. B, B,) which] takes the place of a first stomach, and prepares the swallowed food for digestion. In GryUotalpn it occurs as a perfectly sack-shaped appendage of the oesophagus * (PL XXI. f. 7-)- To facilitate this the inner surface of the crop is covered with glands (for example, in Dyticus, Blatta, &c.), the secretion of which has the func- tion of a preparing juice. Such an expansion of the oesophagus before the proventriculus might readily be considered as analogous to the crop of the higher animals, of the birds, for example; an opinion which Ch. L. Nitzsch has already propounded-]-. The expansion, however, without a contemporaneous proventriculus, is of a different and peculiar kind, namely, the sucking stomach, indicated by G. R. Treviranus, and which we proceed to describe. * THE SUCKING STOMACH. 103. The Hymenoptera, Lepidoptera, and Diptera are the orders in which the proventriculus is deficient, but they possess, nevertheless, a bladder- shaped distension of the oesophagus (PI. XVII. and XVIII. c, c,), which in the first lies directly in front of the cardia ; in the second it forms a distinct bag, which opens into the oesophagus, contiguous to the cardia; and in the third it hangs appended to the oesophagus by means of a long thin duct, frequently far in front of the opening of the stomach. This organ is the before-named sucking stomach. Its function does not consist in being a receptacle for nutriment, but in promoting the suction of food, by distending, at the will of the insect, and thus, by the rarefaction of the air contained within it, facilitating the rise of See Sucko\v,in Reusing. Zeitschrift. f. d. Org. Php. vol. 3. p. 53. PI. II. f. 134. f Gattungen dcr Tliier-Inseckten, Germar's Magaz. iii. p. 280. 126 ANATOMY. fluids in the proboscis and oesophagus. Insects which chew are natu- rally deficient in this apparatus, or at least in this function of it ; in them it is a true crop. In the Hymenoptera (PI. XVII. f. 10, c,) the sucking stomach is a distension of the oesophagus in front of the cardia, and consequently perfectly resembles a true crop. Indeed, in those families of this order, which possess more a mandibulate apparatus than a suctorial, this suck- ing stomach must gradually become superfluous ; and it is, consequently, so little distinct from the oesophagus that it was formerly always described with it, and as nodose *. It exists however as a distinctly denned organ in the families of the bees and wasps, which possess a true suctorial apparatus ; and here it is a large bag, which hangs below the oesophagus, in front of the mouth of the stomach f. If it be empty it lies folded longitudinally ; when filled with air it is distended as a transparent bladder, and embraces the long funnel-shaped mouth of the stomach, which is furnished at its aperture with valves. In the Lepidoptera (PL XVIII. f. 5.) we find the sucking stomach still more distinctly separated from the oesophagus. In these it projects with a short neck at right angles from the end of the oesophagus, and when simple it lies as a folded bladder contiguous to and over the stomach, or upon each side of it when, as in Zyg&na J, it consists of two equal halves. This division is sometimes unequal, when a smaller bladder hangs beneath the large one . It is always proportionate in compass to the length of the proboscis, so that it completely vanishes when the proboscis dwindles to a short cone, as in Gastrophaga pint and Cossus ligniperda ||. Many Neuroptera, for example, the genera Hemerobius and Phry- ganea, have apparently similar bags, which are likewise inactively folded, but which also admit, like those of the Lepidoptera, of being distended into tight bladders. These organs may possibly be sucking stomachs, particularly as these insects, although provided with a man- dibulate apparatus, take food more by suction (this is the case espe- cially in Phryganea) than by mastication. * For example, in the Tenthredos and Ichneumons, Ramdohr, PL XIII. f. 2 and 3. and PI. XIV. f. 2. f Ramdohr, PL XII. f. 6. PL XIII. f. 1. PL XIV. f. 3. Treviranus, PL XIV. f. 3. and PL XVI. f. 3. * Ramdohr, PL XVIII. f. 1. Trevirauus, PL IX.v,v II Ib. p. 109. THE ORGANS OF NUTRITION. 127 In the Diptera, lastly, (P). XVIII. f. 2 and 3, c, c,) the sucking stomach is still more distinctly divided from the oesophagus, and is a single mouthed bag, having one or several ends, and furnished with a solitary evacuating duct. When empty it is small and wrinkled, but when distended it is of large dimensions. In its natural situation it lies contiguous to and over the stomach, at the very commencement of the abdomen, whence its delicate evacuating duct, rising anteriorly, accompanies the stomach as far as the oesophagus, of the size of which it generally is, and opens into it more or less closely to the cardia *. According to Ramdohr this organ is the food bag (speisesack), as it serves for the reception of food. Meckel calls it, from the same cause, the honey vessel (honigbehdlter), and he found in it a peculiar, coloured liquid. But Treviranus' representation is much too illustrative, and his investigations in insects opened alive much too conclusive to admit of the least doubt being entertained of the function of this organ. The Hemiptera, which likewise live upon imbibed juices, have no sucking stomach, nor any analogous apparatus ; this is the case also in the Pupipara and the flea, although they must necessarily be classed among the Diptera f. THE PROVENTRICULUS. 104. The PROVENTRICULUS (PI. XVII. f. 8 & p. 21, f. 810) is the third division of the intestinal canal, if we may consider the crop or sucking stomach as nothing but a distension of the oesophagus. It is a small narrow and tubular cavity, much folded within, and furnished with teeth, spines, or projecting horny ridges. It lies directly in front of the mouth of the stomach, and as which it may properly be con- sidered. It is found in all mandibulate insects which feed upon hard substances, or require the comminution of their food previous to digestion; consequently in all the carnivorous tribes (Carabodea, Hydrocantharid.es, Brachyptera), the wood-beetles (Cerambycina, but here somewhat altered), many Rhinchophora , the Orthoptera, (with the exception of the Phasmce and the Grylli, whose whole crop is furnished with spines which serve to triturate the food), and the Neuroptera. Exteriorly it has always a round somewhat ovate appear- * See Ramdohr, PI. XVIII. XXL, and Trevir.Pl. XVII. t See Ramdohr, PI. XXI. f. 6., and PI. XXIII. f. 2. 128 ANATOMY. ance, and is compact, opaque, and more distinctly muscular than the rest of the intestinal canal. It consequently answers to the gizzard of the gallinaceous birds, an analogy which still 'more strongly confirms the general analogy of organisation existing between insects and birds. A closer anatomical investigation of this organ displays two very distinctly-separated membranes, the exterior of which is tight and muscular, and the interior folded, smooth, and partially horny. The folds of the inner membrane are by no means accidental, but perfectly regular and differently formed in the several families. In the preda- ceous beetles (Cidndelacea and Carabodea, Pi. XVII. f. 8), four is the prevalent number. Four large arched folds, densely covered with short horny spines, bend inwardly in the cavity of the organ, and between these lie four smaller ones, which are sharply ridged in front. Within the large folds there are four robust bundles of muscles, which unite above and below, and thus form a closing muscle at each opening. The similarly constructed mouth of the stomach in Stapkylinus has five large folds and as many small ones. In Cryptorhynchus Lapathi there are nine equal prismatic folds, from the inner ridges of which originate two rows of diverging horny processes, which meeting from fold to fold, separate a central star-shaped space from the entire cavity *. In the Capricorn beetles (Cerambycma) there is no cavity at all, but at the inner margin of the cardia there are four large and four smaller horny plates (PI. XXII. f. ], Lamia cedilis}. The Ortkoptera (for example, Acheta,) have six chief plates, which are covered with scale- shaped horny plates. In the Termites (PI. XXI. f. 8 10.) I disco- vered a proventriculus, which consisted of a ring of twelve equal broad folds, between which again twelve finer and sharp edged ones lay. Around this ring, which formed the central girdle of the cavity of the organ, there were six strong fasciculi of muscles, which united above and below like the ribs of a gothic arch, and thus formed closing muscles. In Blatta, instead of folds we find hooked horny teeth, which spring from a broad base at the sides of the stomach, and project into its cavity. In Gryllus migralorius (PI. XXI. f. 1 6.) I found no proventriculus, but the entire pharynx and crop were armed with rows of small but differently sized teeth, which, running longitudinally, formed in the centre transverse waved lines, but towards the cardia again stand in twos and threes upon elevated mus- * Ramdohr, PI. X. f. 14. THE ORGANS OF NUTRITION. 129 cular ridges. The cardia itself was armed with six Y-shaped horny teeth (PI. XXI. f. 6. a, a). In Muller's representation of the intes- tinal canal of Phasma no proventriculus is visible *, I consequently surmise they would present a similar structure. The exterior skin of this organ is tense, not folded, and it closely incloses the interior one as a similarly shaped distended bag. It agrees in structure with the muscular membrane of the intestinal canal. The space between both is occupied by fasciculi of muscles, and the spongy layer or middle membrane must necessarily be deficient here as well as in the crop, it being the produce of digestion, and therefore can only be present where this has commenced. The larvae of all the above-named insects whose metamorphosis is complete, entirely want this organ, and in them the pharynx passes immediately into the considerably wider stomach. We do not either observe in the very voracious caterpillars of the Lepidoptera any further comminuting stomach. 105. THE STOMACH. The stomach (ventriculus, PI. XVII. XXII. D, D), according to most entomologists, is that portion of the intestinal canal which extends from the end of the oesophagus, or of the crop, to the opening of the eva- cuating ducts of the biliary vessels. Straus, Treviranus, and Joh. Miiller -f- call it the duodenum, as digestion commences in it, in those orders which have the proventriculus, and perhaps this interpretation may be more correct than that hitherto used. Upon examining the form of this portion of the intestine it soon becomes apparent that it is subject to many changes ; it always approaches more or less to the tubular, but it at the same time distin- guishes itself from the following divisions of the canal by its greater compass. The shorter the stomach is the further does it recede from the tubular form, and approaches to the ovate, conical, or bladder- shaped. The Lepidoptera (PI. XVIII. f. 5. D) have the smallest stomachs of all insects. In these it takes the shape of an egg, the ends of which contract into narrow tubes, and its upper surface is folded in irregular * Nova acta Phys. Mecl. n. cur. T. 12. B. PI. L. f. 2. f Job. Miiller de Glandul. Secern. Struct. Pen. p. 68. Lips. 1831, fol. K 130 ANATOMY. constrictions. Generally, upon both upper and under surface, a narrow sinewy or muscular stripe runs longitudinally, for the purpose of strengthening the there more delicate envelope. Meckel informs us * that this stomach in Acheronlia Atropos is shaggy externally, a solitary instance of this structure in the Lepidoptera. The longitudinal, more tubular, and regularly transversely folded stomach of the Hymenoptera (PI. XVII. f. 10. D) approaches very closely in structure to that of the Lepidoptera. It commences with a funnel- shaped orifice, which is evidently analogous to the before-described proventriculus, and as such projects into the cavity of the sucking stomach, which can be closed by valves that open inwardly f- This funnel-shaped orifice facilitates the passage of the food from the oeso- phagus into the stomach, its aperture being thereby brought nearer to the former, indeed, during suction, rising quite up to it ; the valves however preventing the return of the chyme into the sucking stomach. This structure of the stomach is found in all the Hymenoptera, but it varies much in compass ; in some (Sirex) it is short, broad, and straight, the crop, on the contrary, is very long and nodose ; in others (Chrysis) it is distended in the middle and recurvate at the extremity ; in the bees and wasps it is of tolerably equal breadth, but not straight, for it bends inwardly at both ends, so that it is partially inclined towards the axis of the body. In the larvae of these insects the whole intestinal canal (PI. XVII. f. 9. D) consists but of this transversely folded stomach, and all the fol- lowing divisions, including also the anus, are deficient : this stomach, consequently, is more compactly constructed in them than in any other insect, it being composed of five skins, whereas the others have but three. It is probable that both the mucous and muscular membranes have separated into two layers J. In the Diptera (PI. XVIII. f. 3. D) the stomach is a long tube, which frequently distends at the two extremities, and is narrowest in the centre (Musca); a callous ring is found at the cardia, which is the remains of a small bladder existing there in the larva state ; the vicinity of the cardia is granulated, that is, uneven, arising from transverse and longitudinal striae. Some of the large group (perhaps all), which Latreille calls the Diptera Alhericera, have peculiar, glandular, * Verglci. Anatomie, vol. iv. p. 87. f Compare Treviranus, Vermischte Schriftcn, vol. ii. PL XV. f. 2. J Compare Suckow,in Heusinger Zcitschr. f. (1. Org. Phys. vol. iii. p. 18. PI. VI. f. 131. THE ORGANS OF NUTRITION. 131 secretory organs which evacuate themselves at the very commencement of the stomach, closely behind the cardia *. They are doubtlessly the same forms we shall more fully describe below in the Orthopterja, and which have been considered as the analogues of the pyloric caecum of the pancreas, or liver. The Neuroptera have a short, sometimes smooth, sometimes trans- versely striated cylindrical or conical stomach, in front of which, at least in Myrmecoleon and Panorpa, there is a distinct proventriculus. This is wanting in the Libellulee and Ephemerae: their stomach is long, cylindrical, and separated from the pharynx by a slight con- striction only. Lepisma, which genus, as well as the two families of Termites and the mandibulate parasites, I unite in the order Dicty- otoptera, has a very small stomach, and in front of it a proventriculus armed with six teeth, contiguous to which lies a broader and larger crop. The same is the case in the Termites, but their stomach is longer. The Mallophaga t have also a tolerably large crop, but the true stomach is small, and is provided beyond the cardia with two con- siderable points ; perhaps they, as well as the genus Psocus, for both devour hard materials (the former, for example, feathers), are also furnished with a proventriculus. The three remaining orders display stomachs of a much more complex form than the preceding. In the Coleoptcra we find a considerable variety in the structure of the stomach, we observe the most simple in those Lamellicornia which feed upon feculent substances, or upon the juices of flowers (for ex., Scarabcens, PI. XX. f. 2., Melolonlha, Trichius). In these the short and narrow oesophagus passes, without any distinct indication of its termination, gradually into a very long, cylindrical, and equally wide stomach. The object of this great length of the stomach is evidently to prepare the food more fully for assimilation, for in the larvae of these insects it is much shorter, but in compensation it is supplied at both ends with blind, pointed appendages (organs of secretion), of which, in some cases (for example, Ulster, a genus closely approximate to the Lamellicornia,} traces still remain in the perfect insect. Next to these, the tribes which feed upon fresh vegetable matter, and parti- cularly the juices of flowers, the Chrysomelina and Cerambycina, have * Bombylius, Leptis, Chrysotoxum, see Ramclohr, PL XX. and XXI. f Ch. L. Nitzsch, in Germar's Magaz. der Entomol., vol. iii. p. 280. and vol. iv. p. 277. K2 132 ANATOMY. the most simple stomachs ; in these also it is a long, tolerably broad, smooth tube, which rarely (for ex., in Chrysomela,} is beset with short flocks. These flocks are portions of the internal mucous membrane which pass through the muscular membrane, but are not covered by it. In some genera (for ex., Lema, Callichroma moschatum,} portions of this tubular stomach are broader, others again narrower, but in the majority it gradually decreases in size. . The structure is more anomalous in other families, which, although chiefly feeding upon vegetable matter, consume it in a more crude and unprepared state, viz , as fresh leaves or harder fruits. The majority of these have also a long, cylindrical stomach, but the oesophagus is divided from it by a distinct muscular ring, and it is more tense, and occasionally, as in the Hymenoplera, transversely ringed. Among these are the Rhynchophora, many of which even possess the proven- triculus and the before-mentioned flocks, (for ex., Cryptorhynchus La- pathi}, the Vesicifica (as Lytta, Mylabris, Mcloe), the tortoise-beetles (Cassidaria), &c. But the Buprestidea, of all the vegetable feeders, exhibit the most remarkable structure of the stomach : in these, at its very commence- ment, it distends on each side into a long blind appendage, equal indeed in length to the stomach itself; and this appendage, as well as the commencement of the stomach, is furnished throughout three parts of its extent with short, blind processes, like that of the flesh feeders. The remainder of the cylindrical stomach is smooth *. The Elaterodea form a transition to this remarkable arrangement, for in them the com- mencement of the stomach has on the two opposite sides a short folded pocket, it then continues, as a narrow, cylindrical, transversely folded tube, and distends widely at its termination t. The Carnivora display the most complex structure of this organ among the Coleoptera (PI. XIX. f. 4. n, D). Here the before-described proventriculus lies in front of the stomach, from which it is separated by a distinct constriction ; the stomach itself is not very long, at least considerably shorter than in the vegetable feeders, and it is covered upon the whole or major part of the upper surface with long, thin, and blind flocks. These flocks originate, as was already observed in Chrysomela, from the inner mucous membrane of the stomach, and * Compare H. M. Gade, in the Nova Acta Phys. Med., vol. xi. part ii. p. 329. ; and J. F. MeckeFs Beitriige zur Vergl. Anat., vol. i. pa-t ii. p. 129. t Ramdohr. PI. XI. f. 1. THE ORGANS OF NUTRITION. 133 pass through the exterior muscular membrane, the filaments of which it pushes on one side. They doubtlessly consist of secerning organs, whose secretion makes more soluble the heavily digestible animal matter. These flocks are found in the Cicindelacea, the Carabodea, the Hydrocantharides, the Brachyptera, the Peltodea, the Melanoso- mata, and the Helopodea. The stomach of the majority of the Orthoptera is still more artifi- cially constructed, although in many respects not dissimilar to that just described. They equally have a crop and proventriculus, the stomach itself is not very long, but tolerably broad and most frequently transversely ringed above; at its mouth there are broad, sack-shaped, blind appendages, which are not mere processes of the mucous membrane, but are also covered by the layer of muscular mem- brane. There are two such appendages in Acheta and Gryttotalpa, and as many in Locitsla, but here shorter, and more vesicular. In Gryllus migratorius I found six tubular ones (PI. XXI. f. 6.) length- ened above and below, each of which opened into the stomach by an oval aperture (the same A, A, A,) and thin tubes, which lay convo- luted in the tubular appendages passed into these openings from the internal membrane of the stomach (the same fig. 5.) ; consequently these apertures do not merely open into the stomach itself, but alse between the innermost and central membranes of the stomach (see fig. 2. at the * ). In Blatta there are eight such appendages, four short and four long ; these are also, without doubt, organs of secretion, which have been not inappropriately compared to the blind appendages in the pylorus of fishes. They would thus be analogous to a gastral salivary gland, or pancreas. We have yet to examine the stomach of the Hcmiptera, which is the most composite of all (PI. XX. f. 3). The narrow, and generally long oesophagus suddenly distends itself upon its entrance into the abdomen into a broad, bladder-shaped, generally long, and often irre- gularly folded stomach (D), which is, without doubt, analogous to the crop of the other orders. The Hemiptera which imbibe raw juices, either animal or vegetable, require several successive stomachs for the gradual transformation of these substances. The first of these stomachs serves as a preparatory receptacle, wherein the materials accumulate, and where they are slightly changed, that they may be more effectively elaborated' in the following divisions. This first stomach is consequently the widest of all, and thus corresponds to the crop of the Cuicoptera 134 ANATOMY. and Orlhoptera. With respect to its precise form, it is smooth and cylindrical in Nepa, somewhat wider and transversely ringed in Lygteus, shorter but wider, with irregular longitudinal folds, which form apparent large pockets, in Cimex. In Cimex rujipcs two com- pact,; round, transversely ringed bodies lie above, contiguous to the cardia, one upon each side of it. In Cicada the first stomach is short, but also very broad and bladder-shaped. The second stomach (D *) is in general the narrowest, but always the longest ; it has the appearance of a compact muscular tube, whose function can be no other than the further preparation of the imbibed juices ; it is consequently of a more solid structure, and indeed in Nepa * it is internally covered with ele- vated ridges, which form a reticulation of hexagonal cells. Its function and even structure therefore correspond with the proventriculus; it more triturates the food than extracts it. It is separated from the following stomach by a perfect sphincter, and sometimes is distended in front of this into a large bladder (D**, Cimex rujipex, C. baccarum), which must not be considered as a proper stomach but as a second receptacle for the triturated matter, as a second crop before the third stomach. This distension, in greater or less compass, appears peculiar to all the bugs, but is wanting in the rest of the Hemiptera. In the Cicada the second stomach is nodose, very wide in front, growing gradually nar- rower behind. The third and last stomach (D***) is in the bugs wider than the second, but narrower than the crop lying in front of it. In form it resembles the transversely striped stomach of the bees, its cavity being formed by four half cylindrical tubes (Cimex baccarum and C. prasinus), and these half tubes completely separate in C. nt/ipcs, so that their third stomach properly consists of four contiguous stomachs t- In many water bugs, Hydrocorides (for ex., Nepa, Nau- coris}, this stomach is wanting, but in compensation the second, as well as the following portion of the intestine, are longer, as in the land bugs (Geocorides). In the Cicadaria (PL XVIII. f. 1. D**) it is of the same length as the second, but of less breadth, while the second (D*) is granulated upon its exterior surface. Separated from- the former by a distinct sphincter, it, like it, gradually decreases and turns upwards into the first stomach, indicated as the crop (D), so that the transmission of the food describes a complete circle in the three * Ranidohr, PI. XXII. f. 8. f Compare O. R. Trevirauus, in the Auualcn clcr Wuttcrausch. Gesellsch. sur Uie Naturgcsch, vol. i. No. ii. THE ORGANS OP NUTRITION. 135 stomachs. The remainder of the intestine is continued at the opposite side of the stomach, and it is there also that the biliary vessels empty themselves. Thus much upon the form of the stomach in the several orders of insects ; with respect to its structure, almost all that can be said upon it has been mentioned above, in treating of the nutrimental canal. The three membranes described there are found also in the stomach, and here particularly distinct. They are here more loosely united than in any other portion of the intestinal canal, and their exhibition is conse- quently attended with no difficulty. The middle membrane is attached more closely to the innermost, and the granules are found in it which Straus (see above, 96.) indicated as gastral glands; between this and the inner mucous membrane the chyle collects, and then transuding through the latter, it enters the abdominal cavity, undulating about all the organs. But little also can be said of the situation of the stomach, as it is not subject to much deviation ; it is always found in the abdomen, whilst the oesophagus, and very generally the crop, are seated in the thorax. As soon, therefore, as the intestinal canal enters the abdomen it becomes the stomach, and frequently, indeed, even in the thorax (Melolontha and many others). If the intestinal canal be only as long as the body, the stomach then lies directly in its axis, but if it be longer, it then makes windings, which are the larger and more numerous the longer and more extended it happens to be. These convolutions generally lie in the anterior portion of the abdomen, encompassed and retained in their place by the ramifying branches of the air vessels, the hinder portion being chiefly occupied by the sexual organs ; the stomach and intestine also approaches closer to the back, the internal sexual organs filling the ventral portion, or the space beneath the nutrimental canal. 106. THE DUODENUM. The divisions of the nutrimental canal which follow the stomach are generally more simple than the preceding, and also subject to fewer changes of form. In breadth they do not generally, with the exception of the last, or colon, equal that of the stomach ; they are mostly nar- rower, and also more delicately constructed. This entire intestine also consists of the three membranes, which, however, often lie more closely 136 ANATOMY. attached to each other, but frequently in the ilium, particularly when the muscular membrane is very delicate (Lamia cedilis} *, they leave a considerable space between them. Here and there also the muscular membrane is thicker than in the stomach, which may possibly be explained by the distribution of similar fasciculi of fibres over a nar- rower space, whereas in those cases in which this intestine is as distended as the stomach (for example, Lamia a'dilis,') the muscular membrane of both is uniform in its consistency. The passage of the stomach into the duodenum is formed by a dis- tinct constriction, which supplants a sphincter, or is possibly one ; the ring thus projecting internally is called pylorus, immediately beyond which the mouth of the gall vessels pierce the intestinal membranes. This intestine is also separated into different divisions by means of constrictions, which have different functions, and have consequently received different names. The first of these divisions is called the DUODENUM according to Ram- dohr, but it is scarcely analogous to the similarly named portion of the intestinal canal in the superior animals, but it more probably entirely belongs to the following ilium. In the few beetles in which it has been hitherto observed (Sitpha, Necrophorus, Melolontha, Lampyris] it generally appears as a short, smooth tube, of equal width, or narrower (Melolontha} than the ilium, from which it is distinguished exteriorly by the ringed constrictions of the latter (Necrophorus^, Silpha J). A stronger ringed constriction separates it from the following portion of the small intestines. 107. THE ILIUM. Wherever the duodenum is wanting the ILIUM (PI. XVII XXII. E, E,) follows immediately upon the stomach, from which it is separated by the above described pylorus. This portion of the intestine is likewise sometimes wanting, so that the stomach lies immediately contiguous to the colon (Libellula\, Reduvius ||). This appears to be the general rule of structure in the bugs; and when even occasionally a small portion of the intestine is found beyond the stomach in which the biliary vessels bury themselves, it is nevertheless so inconsiderable * R^m.lohr, PI. IX. f. 6. f Ib., PI. V. f. 1. : Ib., PI. IV. f. 2. Ib., PI. XV. f. 4. || Ib., PI. XXV. f. 5. THE ORGANS OF NUTRITION. 137 that it may consistently be considered as deficient. This deficiency in them may be accounted for by the number of their stomachs, for that transmutation of the food which is properly the function of the ilium takes place in their third stomach, and which consequently renders the ilium unnecessary. With respect to its structure, we have already indicated some of its >eculiarities in treating upon the membranes of the stomach. Those of the ilium are generally tenser than the latter ; it is invariably equally distended, and, as it were, inflated, whereas the stomach is not un- usually folded up. We have already mentioned that the ilium, as well as the stomach, is frequently transversely ridged, and by this means is distinguished from the duodenum. The length and situation of the ilium varies considerably ; it is rarely so long or longer than the body (Necrophorus), in general shorter, and even shorter than the stomach. The latter proportions are found espe- cially in the Chrysomelina, and in many others which feed upon vegetable matter it is the general rule. In many of the carnivora, for example, the water-beetles (Hydrocantharides^, the ilium on the con- trary, is longer than the stomach, particularly in their larvae, in which it is twice as long ; but this is not the case in the ground-beetles (Cicindelacea and Carabodea}, the ilium in them being not so long as the stomach. The butterflies have the longest ilium, in proportion to the stomach of all insects, for in them it is not merely twice as long, but even three or four times the length of the stomach, which is the more extraordinary as in the caterpillar it is excessively short, scarcely extending to one-eighth of the length of that organ. In the Diplera also it is shorter than the stomach ; in the bugs alone is it sometimes wholly deficient. It is regularly wanting in the Libcllulcc and Ephemera. There are no fixed laws which regulate the length of the ilium, but Ramdohr has endeavoured to show its most prevalent pro- portions to the stomach and the other parts ; they are as follows : the most usual relation to the stomach is as 1:1, or 1:3; to the whole intestine 1 : 5, or likewise 1 : 3. Some of the proportions are extra- ordinary, as in Necrophorus, viz., the ilium to the intestinal canal as 2 : 3, to the stomach as 9 : 4 ; indeed, this beetle has the longest ilium of any yet investigated. In Tenthredo nigra it is very short, viz., in proportion to the entire nutrimental canal it is as 1:17- In the cater- pillars of the butterflies it is always very short, and in general it is 138 ANATOMY. short in all larvae, and it is the shorter in proportion to the extension of the stomach. The situation of the ilium is so far determined that it is always found beneath and contiguous to, and never above the stomach, but its situa- tion in itself varies considerably. In perfect insects it is seldom straight, but always so in those whose intestine is not longer than the body (Gryllus, Phasma, the larvae of butterflies). In the opposite cases it makes convolutions of different size and form, which are the more numerous and larger the more extended the ilium itself is. 108. In some instances the ilium appears under a different form, namely, gradually distended, and thus becoming clavate, which is however peculiar to a few beetles only. According to Ramdohr, who considers a thus distended ilium as a distinct portion of the intestine, it is called the CLAVATE intestine. In the Chrysomelina the short ilium is thus frequently distended. In many of the Capricorn beetles a somewhat distended portion of the intestine is separated by a constriction from the very narrow ilium, and this represents the clavate intestine. In the Lamellicornia (Mclolotilha, for ex.) the clavate intestine appears likewise as a distended sack-shaped ilium, and is therefore called by Ramdohr the THICK intestine. It is particularly distinct and large in the larvae of these beetles (PI. XX. f. 1. r) ; here, namely, it appears as a broad bag here and there constricted, which, in its natural situation, turns back upon the stomach from its commence- ment, and extends as far as the length of the narrow ilium will admit, consequently to the end of the stomach. The bag here contracts, and the again narrow colon originates beneath it, in a bow of it, taking its course in a contrary direction towards the anus. In the perfect beetle (the same rig. 2.) this bag is to be distinguished exte- riorly only as a bellied distension of the ilium, which, at least in Mclo- lo/tt/ia, has five slight impressions. But if this portion be opened five elevated ridges are observed, which are divided by incisions at regular distances, so that each band appears to consist of short, contiguous, three-sided prisms *. If the name of this portion of the intestine is to be determined accord- ing to its divisional distance from the stomach it must be considered as * Suckow in Ucusinger, vol. iii. PI. . f. 04. Straus Duvckheiui, PL V. f. 8. THE ORGANS OP NUTRITION. 139 the true ilium, which is however contradicted by its function, which, like that of the caecum of the glires of the mammalia, subjects the food to a second digestion and extraction before it is rejected. We are convinced of this by the comparison of its state in the stomach, and in this portion of the canal, for we find it here much more pappy than there, but yet not so viscous as in the colon. 109. THE COLON. The last division of the intestinal canal is called the COLON (PI. XVII. XXII. H, H,). It is divided from the preceding portion of the intestine by a valve which can completely shut its aperture. G. R. Treviranus was the first to describe and figure it *. Its internal surface, particularly near the mouth of the ilium, is thickly beset with glandular warts or flocks, which are not found in the ilium itself. We have observed glands only in the crop, and as their function there was evidently the secretion of the first menstruum of the food, they may here possibly produce a secretion to assist the rejection of the faeces. The COLON generally exceeds the ilium in size, but when the conical or thick gut precedes it it is narrower ; but it then is even longer than the ilium, which is not usually the case. The form of the COLON varies, sometimes cylindrical, or clavate, or distended above (bees); sometimes sack- shaped (Carabodca) , or longitudinally folded within (caterpillars and the larvae of Calosoma). These folds are produced by the internal intestinal membrane, and are either straight or waved, and supported by horny ridges. The muscular membrane does not assist to form these folds, but it is more compact and firmer than in the preceding portions of the intestine, yet the above described thick gut or occasional analogue (by situation) of the ilium is frequently much more fibrous. The colon is also occasionally fenestrate, that is to say, there are six ovate transparent spots in it which are surrounded by a horny margin or edge, and form either one or two rows, varying in situation, so that the spot in the lower I-OAV lies where in the upper one is found the intervening space. This structure Suckow first observed in the bees f. I found in Harpulus riijicornis a perfectly similar structure of the colon, these fenestral spots were in the internal * Vcriuischtc Scliriftcn, vol. ii. p. 105. PI. XII. f. 3. t In Hcusingcr Zeitschr. f. d. Org. Ph., vol. iii. PI. VI. 140 ANATOMY. membrane, and were very bright and transparent. According to Ramdohr's observations, the width of the colon is in proportion to that of the pharynx (crop), for where the latter is broad so is also the colon, and vice versa. The situation of the colon is always determinate, for it is always found at the apex of the abdomen, surrounded by its last segments. The evacuating opening, or ANUS, is found in the last segment itself; it is covered above by a peculiar valve, and beneath this the anal vessels, which we shall describe lower down, open themselves. The corresponding lower valve conceals the sexual aperture, so that both the anal and sexual apertures open into one cavity, which might be called the CLOACA, and which are separated only by a fold if no other organ, for example, an ovipositor, be present. The anus, as well as the ilium and its correspondent the thick gut, are wanting in the larvae of the bees, wasps (PL XVII. f. 9.), the Formicaleo, and of perhaps all the internal parasites, for example, the Ichneumons ; their intestinal canal consisting of the pharynx and stomach, and a small bag beyond it, into which the biliary vessels open themselves ; it is here that the faeces collect, which are evacuated upon the perfect insect quitting the pupa state, when it is provided with an anus. 110. THE CAECUM. In many insects we find, in connection with the colon, a blind, sack- shaped appendage, or rather similarly shaped superior distension of it which we call caecum (PI. XIX. f. 3 and 4 G, G). It originates at the very commencement of the colon, contiguous to its connection with the ilium, and extends anteriorly towards the stomach, in either larger or smaller distension; it is consequently not separated from the colon by any constriction or valve, but both cavities are in immediate connection with each other. This, as well as their uniformity of structure, proves that it must only be considered as a distension of the colon. In form this caecum is sometimes nodose (Stlphu) and directed forwards, some- times laterally distended (Necrop/wrus) , sometimes it is a long tubular point ( Dyticus}, sometimes a shorter cylindrical process of equal width with the colon (^Nepa), similar to this, but sometimes slightly con- stricted at its commencement, we find it in the butterflies. It thence appears that this portion of the intestine is more peculiar to the car- nivorous tribes, as Ramdohr, somewhat justly, remarks ; yet its struc- THE ORGANS OF NUTRITION. ]41 ture in the nectar-sucking butterflies modifies this assertion. The caecum might also here, as in the Mammalia, have the function of a second .stomach, and thus, therefore, be more serviceable to the car- nivora, which consume coarser materials than the vegetable feeders, which are besides provided sometimes (Melolonthu, &c.) with ana- logous organs, as the clavate and thick intestine. The caecum is repre- sented in the Carabodea by the broad sack-shaped colon. The long caecum of the water-beetles has, according to Leon Dufour, the func- tion of a swimming bladder, which is much to be doubted in the Cole- oplera, they being provided with so many air vessels : we cannot either well imagine how air can be introduced into it, certainly not through the anus ; for it is not for this purpose that water-beetles raise their anal ends to the surface of the water, but to take air beneath their elytra, as has been long well known. 111. THE BILIARY VESSELS/ The BILIARY VESSELS (vasa billfera, (PI. XVII. XXII. K, K,) occupy the first place among those organs which, although distinct, stand however in direct connection with the intestinal canal. They are narrow filiform tubes, which open at one end into the duodenum, and where this is wanting into the ilium close behind the pylorus, and at the other end are either free and closed, or pass into each other and thus apparently form one vessel, which pierces the intestinal membranes with both its ends. The biliary vessels also, at least according to Ram- dohr, sometimes empty themselves into the end of the stomach, some- times (for example, in Meloe,) upon the limits of both, that it is difficult to say whether it is the stomach or intestine. According to Ramdohr, the mouth of the biliary vessels does not pierce the internal intestinal membrane, but only the exterior muscular one, which assertion, however, is contradicted by Meckel's observation, for, by pressing these vessels, he forced their contents into the intestine. In fact, the biliary vessels always enter the cavity of the intestine, and their mouths lie at the same height, forming a circle around it; more rarely upon one side only, for example, in a vesicular disten- sion of the ilium in Lygceus ap/erus. Other differences in the mode of their evacuating themselves are not rare. In the flies (Muscaria') the four biliary vessels unite into two short stems, which open into the intestine at its opposite sides, or all four form but one, as in Cimex * E Salv^AU, ^ j#, t "'' 3o ,J. JT8; (,> . 142 ANATOMY. baccarum. Occasionally, also, the openings of the gall vessels do not lie by the side of but above each other, for example, in some of the Neuroptera, in which four of the eight biliary vessels enter upon the one side and the other four upon the other side of the intestine (Myr- mccoleori). If many biliary vessels exist their mouths lie contiguously, above and below each other, or although more rarely, all upon one side (Acliet(i), or else they unite into a tolerably long evacuating duct, (for example, Gryllotalpa). In form these vessels are generally narrow, cylindrical, filiform, and twisted, but they are not always of the same dimensions throughout : many commence narrowly and afterwards double in size; some, by means of a spiral furrow, resemble a turned slip ; others have alternately small vesicular distensions (Musca) ; a few have long rectangular pro- cesses, which are occasionally furcate (Melolontha vulgaris). There are generally FOUR in number, never fewer, unless entirely wanting (Chermes, Aphis), sometimes there are six or eight, and they are even, occasionally, innumerable. These differences in number are regulated by the order to which the insect belongs as well as by its food, whether it be vegetable or animal, as is shown in the following table : I. No biliary vessels, Chermes, Aphis. II. Few (4 8) biliary vessels. } . Four biliary vessels. a. Free at the end; most Diptera, as well as the families Termiiina, Psocina, and Mallophaga, of the order Dictyoloptera. b. Anastomosing ; many Coleoptcra, Hemiptera, and Diptera. 2. Six biliary vessels. a. Anastomosing ; many Coleoptcra, for example, Ce- rambycina and Chrysomelina. b. Free at the end, Lepidoptera. 3. Eight free biliary vessels, Neuroptera. III. Many biliary vessels, Hymenoplera, Orthoptcra, and the Dic- tyotoptera subnlicornia. Occasionally the biliary vessels join the intestinal canal at a second place, but this union takes place only with the exterior muscular mem- brane, for it is attached by means of solitary fibres, but a second open- ing into the intestine does not occur. This union is found chiefly in those insects furnished with a clavate intestine (the analogue of the THE ORGANS OF NUTRITION. 143 ilium), for example, the Cerambyclna, most of the Neuroptera, and the Cicadaria. The length of the biliary vessels is in direct proportion to their num- ber, for when there are but few they are very long, indeed the longest of all (for example, Melolontha) ; but they are short, on the contrary, where they are numerous, for example, in Gryllotalpa, Libellula, &c. The long biliary vessels lie generally around the intestine ; they first ascend parallel to the stomach as far as the pharynx, they then return and form a thick knot of vessels around the ilium ; where there are many, some return upwards along the stomach, and the rest below along the ilium. The length also of the single biliary vessels sometimes varies, for example, in the Cerambycina, in which they form concentric circles, but the two opposite sides are always of the same length. The biliary vessels are also always more simply constructed than the intestinal canal, for they appear to consist of but a single skin, which, besides, is very delicate and transparent, so that their contents can be distinctly recognised as a finely granulated mass. The delicacy of the smooth shining case is proved by the difficulty of removing the biliary vessels from the enveloping fatty substance, and by their being very easily torn, even when the greatest precaution is used. In colour they generally resemble the yellowish white of the intes- tinal canal ; in some beetles (for example, Carab^ls, Dyticus,} they are of a dark brown, but which becomes paler as it approaches the opening. In many caterpillars, while parallel with the stomach they are whitish, but at the intestine of a saffron yellow ; Swammerdam thence applied the name of saffron vessels to them. It may be here remarked, at the close of our observations upon the biliary vessels, that some insects in which they are numerous, for example, the bees and wasps, have in their larvae state but few (4 6) long and thick ones, which, by degrees, whilst during the pupa state the remaining gall vessels are forming, shrink up, and become shorter until they contract to the same length as the rest *. Do they not perhaps entirely disappear, and are replaced by the shorter ones ? Perhaps they are very different vessels possessing a different function, which probably disappears when the intestine and anus become formed in the insect. * See Raradohr, PI. XIT. 144 ANATOMY. 112. THE SALIVARY VESSELS. Cuvier says, in his " Comparative Anatomy," that the secretory organs of insects always assume a tubular form, and that consequently conglomerate glands are wholly wanting in them. This assertion is strictly true with respect to the biliary vessels, which have been con- sidered as analogous to the liver, but in the salivary vessels we find exceptions, and which are most strongly exemplified in the testes, some of which (the epidydimis in Hyrdophilns) possessing many accumulated acini. Nevertheless, the form considered by Cuvier as universal is cer- tainly the most general. Under the name of salivary vessels we comprehend those glandular appendages of the nutrimental canal which evacuate themselves either into the mouth or into the commencement of the intestine in front of the stomach, and by their secretion promote the digestion of the food. The following are their chief differences : A. Salivary vessels which open into the mouth, generally beneath the tongue, and more seldom at the base of the mandibles. They take the following forms: 1. As simple, long, undivided, twisted tubes ; thus in the ma- jority of insects, viz., all butterflies, many beetles and flies. 2. As a narrow vessel which empties itself into one or two blad- ders, whence the salivary duct originates (Nepa, PI. XXII. f. 1 ; Cimex, PI. XX. f. 3. A, A; Sarcophaga). 3. As a ramose vessel with blind branches, (Blaps, PI. XXII. f.3). 4. As two long, cylindrical pipes, which unite into one evacu- ating duct (Reduvius, PI. XXI. f. 15). 5. As four small, round bladders, each pair of which have a common duct (Pulex, PI. XXI. f. 16; Lygceus, Cimex). 6. As a multitude of such vesicles in Nepa (PI. XXII. f. 2). 7. As capitate tubes, in the free ends of which many very fine vessels empty themselves (Tabanus, PI. XXII. f. 4). 8. As tubes which at intervals are surrounded by twirling blind bags (Cicada, PI. XXII. f. 5). 9. As granulated glands which on each side unite into a salivary duct, both of which join into a single evacuating duct (Gryl- THE ORGANS OF DIGESTION. 145 his, PI. XXI. f. 12.). J. Miiller observed such granulated salivary glands in Phasma ; Treviranus in Apis ; and I have found them in Locusla, Gry/lns, and Termes. B. The salivary vessels which do not empty themselves into the mouth, but into the commencement of the stomach. These we have already partially described, in treating of the stomach ( 105), as short or long bags, which were either simple or fur- nished with processes (Buprestis} other forms, as well as those just cited, are found chiefly among the Diptera. 1 . As two capitate tubes, in the free ends of which many delicate vessels open, we perceive them in Hemerofrius perla (PI. XXII. f. 4). 2. As two short processes of the same width as the stomach, in Leptis (PI. XXII. f. 6. a, a,) and Acheta. 3. As two bags covered entirely with short blind processes in Bombylius (PI. XXII. f. 7.) and Buprestis ( 105). 4. As triangular processes, each edge of which is occupied by a row of vesicles in Chrysotoxum (PI. XXII. f. 8). 5. As six narrow tubes, which surround the commencement of the stomach in Gryllus (PI. XXI. f. 1 and 6). 6. We also consider the blind processes which clothe the stomach in the predaceous beetles among the salivary vessels. Salivary vessels which open into the mouth are found in all the haustellate and in many mandibulate insects which feed upon hard sub- stances. Ramdohr was the first to observe them amongst the beetles in Cryptorhynchus Lapathi. In this insect he found a long twisted vessel, which opened into the mouth, which is indeed contrary to all analogy, for the salivary vessels are elsewhere found in pairs. Leon Dufour subsequently discovered salivary vessels in many Heteromera, viz., (Edemera, Mycterus, Mordella, &c. I have found them of the above form among the Orthoptera, in Locusta, and Gryllus, and among the Dictyotoptera in Termes. Among the Neuroptera, Hemerobius and Phryganea exhibit salivary organs. The salivary organs which empty themselves into the stomach are found among the beetles, especially in those which devour flesh and wood ; and in those Orlhoptera also which feed upon hard vegetable matter, and in the Diptera, among the Syrphodea, which consume the nectar of flowers, and probably also their pollen. Among the grasshoppers we occasionally find both kinds of salivary organs. L 146 ANATOMY. Where we meet with salivary vessels we generally find two ; some insects have, on the contrary, four, each pair of which unite into one evacuating duct (Apis, Cimex, Pulex) ; Nepa has even six salivary vessels, three on each side, all of which open into the cavity of the mouth ; two unite on each side into one stem, the third, which has been considered as a poison-secreting organ, remains separated as far as the mouth. Many larvae, particularly the caterpillars of the Lepidoptera, have also four salivary vessels of diiferent structure ; two are slender, very long (Cossus), and filiform ; two broader, sometimes bag-shaped (for example, Cossus ligniperda, O.), and considerably shorter. The first secrete a viscous liquid, from which the caterpillar spins its silk. The evacuating ducts of both unite into one, and open into the under lip, namely, into the canal of the above ( 54) described spinneret. This pipe would therefore be more correctly called spinning vessel. Such spinning vessels are naturally found only in those larvae which prepare a web for their pupa change, such as the caterpillars of the nocturnal Lepidoptera, the larvae of the saw-flies, and of the Phryganodea. It distinguishes itself chiefly by its length and size from the true salivary vessels, which are often very small and insignificant. The true salivary vessels, according to Suckow *, open at the base of the upper mandible with a small warty protuberance (PI. XXI. f. 13), and remain even in the perfected moth ; whereas the spinning vessels totally disappear during the pupa state f . In Myrmccoleon the spinning vessels lie at the anal end of the abdomen, and true salivary vessels have not yet been observed in it +. The structure of this organ appears, according to all investigations hitherto instituted, to be very variable, for sometimes there are two membranes (the muscular and mucous) and sometimes but one. The former vary in consistency, but occasionally are uniform with those of the intestine ; in the latter case they are transparent and delicate, and occasionally granulated or irregular. The length also of the salivary vessels differs much : in some cater- pillars they are two or three times as long as the intestine ; in perfect insects, on the contrary, they are generally shorter, and do not usually * Suckow's Physiol. Unternich. uber Insecten und Krustenthiere, p. 28. PI. VII. f. 32. a. f Ib.p. 29.P1. II. f. 1 10. h. h. + Ramdohr, PI. XVII. f. 1 4. THE ORGANS OF DIGESTION. 147 extend beyond the thorax. It is thence that we detect the salivary vessels, with the exception of the very long ones of caterpillars, only in the thorax. They here lie around the pharynx, crop, or stomach, gene- rally low down in the breast between the coxae of the legs, whilst their meandering evacuating duct, rising from beneath the nutrimental canal, ascends to the cavity of the mouth, and here, after having united with its companion, opens beneath the tongue. Locusta displays this aperture very distinctly. In the bees, in which the salivary organ consists of four granulated valves, the anterior one lies in the head, directly beneath the forehead, before the eyes, and was originally de- scribed by Ramdohr as the organ of smell, but subsequently recognised as the salivary gland. The evacuating duct empties itself into the tube of the proboscideal tongue, and is a spiral vessel resembling the trachea, as Treviranus has described and figured it * ; in Locusta I found it simple, thin, and transparent, but accompanied by a delicate trachea, which followed it throughout all its ramifications and divisions. 113. THE URINARY VESSELS. As the last distinct organ, but which is doubtlessly in strict con- nection with the digestive apparatus, we must take some notice of the variously formed urinary vessels, which empty themselves above the anus. These, like the salivary vessels, are sometimes mere vascular canals, at others glandular bodies which in the latter case unite into one duct, to which not rarely there is attached a vesicular distension the URINARY BLADDER. The duct of the latter is always separated, and never unites to those of the opposite side, and empties itself laterally contiguous to and above the anus, but strictly separated from it by the anal valve. These vessels are found in all the Carabodea and the Hydrocantha- rides, in many Heleromera (Blaps), and again in Bombylius and Leptis, among the Diptera. Ramdohr, who first observed them, drew them to the intestine, and called them anal vessels ; but Leon Dufour subsequently described many of their forms in detail t. In their most simple form (in Harpalus) the urinary vessels appear as reniform bodies contiguous to the colon, whence a short evacuating * Vermischte Schrif., vol. ii. p. 123. PI. XV. f. 1. f Annales des Sciences Natur., t. 8. p. 6. PI. XIX. and XX. L 2 148 ANATOMY. duct extends to the orifice. In Carabus auratus this body is a bunch of small round vesicles ; in Car. cancellatus it is divided into two equal halves, the two short ducts of which speedily unite into one. The urinary bladder, which is wanting in Harpalus, is present in Carabus, has the shape of a fig, and stands almost at right angles with the eva- cuating duct. It is much the same in Cymindis Jtumeralis; in Aptinus three equal ducts open into the bladder, each of which originates from five granulated glands with five branches. In Brachinus the glands are convolutions of shorter or longer, and sometimes furcate filaments. In Chl(E?iius and Sphodrus there are many solitary granules, each of which has a small duct, they all unite into one stem, which then opens into the bladder. In the water beetles (PI. XXI. f. 11.) the portion lying above, and over the urinary bladder, is but a simple, twisted, but tolerably long, although delicate vessel ; the bladder, on the contrary, is round, but not petiolated. It is the same in Bombylius. With respect to the structure of these organs, two membranes are distinctly discerned in the evacuating duct, the interior of which is much less than the exterior; this is constricted by parallel transverse rings. The glands also have occasionally (Chlcenius velutlnus] similar transverse rings, particularly when they are somewhat larger. 114. CHANGES IN THE INTESTINAL CANAL OCCASIONED BY THE METAMORPHOSES. In the preceding description of the nutrimental canal in insects, we have restricted ourselves chiefly to their form and structure in the perfect creature. As, nevertheless, the differences which are produced in the nutrimental canal by their metamorphoses are by no means unim- portant, for the intestinal canal in larvae assumes very generally a very different form, and its changes are subject to peculiar laws, partially influenced by the order to which it belongs, we must not omit taking notice of them as far as is possible in a general sketch, and must there- fore make room here for a description of these transformations. Insects with an imperfect metamorphosis, viz. the Hemiptera, Orthoplera, and Dictyotoptera, have in all their stages a very uniform nutrimental canal. We find in them the same divisions in the same proportions, and even the appendages, such as the salivary and biliary vessels, agree with those of the perfect insect. The whole change, THK ORGANS OK DIGESTION. 149 therefore, which the nutrimental canal undergoes in these orders consists in its lengthening in proportion to the increasing size of the insect, and at the time of moulting it covers itself internally with a new mucous membrane, the old one being rejected by the anus,, or probably absorbed. This changing of the skin in the intestine is certainly remarkable, and proves, as well as the similar phenomenon in cutaneous affections in man, in which the epidermis peels off (for ex- ample, after scarlet fever), the perfect uniformity of the intestinal mucous membrane with the exterior epidermis. The larvae of the Libellulfs alone appear to make a slight exception to the rule of the intestinal canal remaining the same, their's being somewhat larger, particularly broader, than in the perfect insect, and in the latter the respiration of the colon disappearing, which was peculiar to the former. Insects with a perfect metamorphosis, on the contrary, undergo in the intestinal canal, as well as exteriorly, important changes, which, however, refer only to the form, the structure remaining constantly the same. It is true the membranes are originally much more delicate, looser, and admit of being more readily separated, particularly in the stomach, but this difference gradually vanishes. During their larva state the intestine assumes a new skin at every moulting f ; towards the end of this period, and still more during their pupa state, the intestine shrinks, particularly the stomach, and acquires thereby a more compact appearance. It is the divisions of the nutrimental canal and their relative lengths which chiefly vary, but these are regulated by very different laws in the several orders, and consequently demand of us an especial notice. The maggots of the Dipt era (PI. XVIII. f. 2. maggot ; f. 3. fly) have a longer intestine than the flies, but it is the stomach chiefly which occasions this greater length. The sucking stomach is present, but larger, more shortly pediculated, and, besides, there are large cylindrical salivary bags, which in the course of their change transform themselves into filiform salivary vessels. The biliary vessels remain uniform both in number and shape. During the larva state the intestinal canal remains unchanged, but it alters the more quickly in the pupa state ; * Compare Suckow in Heusing. Zeitschr. f. d. Org. Phy. vol. ii. p. 24, &c. f In the larvae without an anus (Myrmecoleon, Vespas, Apis) the old skin remains in the bag behind the stomach (compare . 105.), and is evacuated only after the pupa state through the new-formed anus. 150 ANATOMY. but it is still the stomach only which shortens, until it decreases to scarcely one half of its former extent. In the Lepidoptera, on the contrary (PI. XVIII. f. 4. caterpillar ; 5. imago), the intestinal canal lengthens, but so that here also the stomach becomes shorter but the ilium longer. In the caterpillar the broad, cylindrical, folded, and transversely ringed stomach occupies more than two-thirds of the entire intestinal canal, and this is succeeded by a shorter, scarcely narrower ilium ; the preceding pharynx is short, and so short that it is observed only in the head. Contiguous to the stomach lie the long twisted spinnerets, and attached to it are the six united biliary vessels. In the imago the pharynx is long, and beneath it lies the sucking stomach, of which we observe no trace in the cater- pillar ; the stomach, on the contrary, is small, short, ovate, folded, and narrow ; the ilium, again, long, filiform, twisted ; the colon broader, elongated above into a short caecum, which is likewise deficient in the caterpillar. The spinnerets disappear, but the salivary vessels, which are very small in the caterpillar, become more distinct, larger, and longer. We have already noticed the very interesting metamorphosis of the intestinal canal in the wasp and the bee. In the order of the Hymeno- ptera also the law prevails of the stomach becoming smaller and nar- rower whilst the pharynx and ilium become longer. This will also apply to Myrmecoleon, in whose larva the colon becomes the spinneret. But of all the orders the Coleoptera display the greatest changes of the intestinal canal. The larvae of the carnivora wholly want the folded horny orifice of the stomach (PI. XIX. f. 1 and 3). Their stomach is broad, but smooth, and not beset with filamentary processes ; the ilium is also broad, but short, and much shorter than after the metamorphosis. This consists in the crop distending, the proventriculus forming itself, and the stomach sending forth filamentary processes. In the Cara- bodea the ilium becomes much longer ; but in the water beetles, where it is already very long, it appears to become somewhat shorter, at least in Dyticus marginalia, according to Dutrochet, whose investigations I have repeated, and can now confirm (see PL XIX. f. 3. the larva ; f. 4. the beetle). In the vegetable feeders, namely, in the Lamelli- cornia, the intestinal canal in the larvae is triflingly longer than the body, whereas in the perfect insect it is three or four times as long. The larvae have a long, broad, cylindrical stomach beset with filaments THE ORGANS OK DIGESTION. 151 at its commencement and end ; a short, narrow ilium ; a broad., sack- shaped thick-intestine ; and a tolerably long but not broad colon : the beetles have a very long but narrower cylindrical stomach, an ilium resembling that of the larvae, a much narrower, gradually distending, thick-intestine, and a longer cylindrical colon, which distends very widely close to the anus. In both cases, consequently, the intestinal canal is longer in the perfect state than in the larva, but in the vege- table feeders more considerably so than in the carnivora, in which it, namely in Dylicus, is shorter. Whereas the beetle has a much more complex intestine, and more organs to effect the change and trans- formation of the food than the larva, which is the more remarkable, as both, at least generally, take the same food, which is not always the case in the other orders, for example, in the Lepidoptera and flies. 115. II. THE FATTY MASS, OR RETE. The fatty mass of insects is a web of generally white or yellow ragged or stringy substance interwoven in every possible way, enve- loping the intestinal canal and the organs connected with it, as well as all the other internal parts, but it is never in direct immediate connec- tion with any organ. It receives its name from its undeniable resem- blance to the fat of the higher animals, and which is expressed in the above peculiarity, and even more strongly in other circumstances. It thence appears that it forms no portion of the intestinal canal, being no- where in connection with it, but as it is the produce of digestion and as it is increased or decreased by the perfection or imperfection of the function of digestion, it must therefore, as standing in relation to the organs of nutriment, be treated of and described when treating of them. We are the more strongly impelled to this by the opinion expressed by Oken, and which Treviranus has recently supported by analogies, that the fatty mass of insects must be considered as their liver. Indeed in the scorpion a substance similar to the fatty mass stands in connection with the nutrimental canal by means of vessels, but they possess besides two twisted biliary vessels, which likewise here and there quit that substance. In all true insects, however, we find no such close connection of both organs, and if it cannot be denied that the fatty mass is of importance to digestion, and that much nutrimental matter is derived from it, yet this admission proves by no means its analogy to the liver. In fact, it is neither absolutely liver nor gland, but 152 ANATOMY. nutrimental matter, which, during the metamorphosis., particularly during the pupa sleep, is absorbed like the fat of the lethargic mammalia during their hybernation. But the degree of reference the function of the liver has to the preparation of the fat is sufficiently well known from the example of the lethargic mammalia, therefore the above opi- nion, when we consider the small size of the biliary vessels supplanting- the liver, or the treatment of these vessels as kidneys, a view also recently promulgated, may possibly have many supporters. The nature of this fatty body is in so far uniform that it consists of shreds, which upon microscopic investigation are found to be constituted of small globules of animal aboriginal matter. This is the only cha- racter this fatty mass presents upon the closest investigation ; exteriorly it is surrounded by delicate membranes, which consequently may be compared to the membranes of the cellular texture, but the lens does not show it very distinctly, from its transparency, delicacy, and tex- turelessness. Ramdohr, who considered the fatty mass as plastic lymph, obtained from experiments upon that of the Gastrophaga quercus the following result: it melted in boiling water, effervesced with sulphuric acid, at the same time smelling like burnt horn, and in cold water was precipitated in white flocks; heated over a lamp it hardened into a white firm mass, swelled up upon the application of greater heat, and then burnt away, dispersing a stinking vapour. According to my experiments, made with the large flabby fatty mass of Cossus ligni- perda, it melted in a spoon over a lamp into a perfectly clear trans- parent yellow liquid, which paper instantly absorbed, and was rendered transparent by it like fat ; it had a peculiar smell, like that of freshly opened caterpillars ; its taste was fatty and insipid. Upon increased heat it boiled up in bladders but did not become firm, or else it consumed to ashes. Laid fresh in hot water it became softer, more transparent, and particles of it floated on the top like oil. These very contradictory results tend at least to prove that the fatty substance in different insects consists of very different constituents, which is the more striking as both experiments were made from insects of the same order, in which they even approach very near each other. Pro- bably Ramdohr's caterpillar had been long immersed in spirits of wine, thus consequently, and by the additional influence of heat, the fat parts had separated, and only the cellular portion of the enveloping mem- branes remained. The entire fatty mass forms a reticulated meshy web, which enve- THE ORGANS OF DIGESTION. 153 lops the interior organs and completely fills all portions of the cavity not occupied by them. In larvae the threads and laces of this net are larger and more ragged, particularly in the fat larvae of the crepus- cular and night moths. The nearer it approaches the pupa state the larger are the proportions of this substance ; but as soon as the insect becomes fully developed this material loses its size, and it becomes a broad, delicate, laced web. It is consequently during the pupa state that the greater portion of this substance becomes absorbed, whereby the shreds shrink up, the delicate membrane becomes narrower, and thus the preceding coarse shreds become delicate and fine laces. In this shape the fatty mass not merely represents the rete of the vertebrata, but actually becomes it, for it is the envelope of the intestines, and in conjunction with the air vessels it supports and fixes them. Thence is it that earlier (Malpighi) and more modern (Cuvier) anatomists have called it the net of insects. It is scarcely necessary, after such facts, to adduce other reasons in opposition to the above disputed opinion that this net is the liver of insects ; whoever has but watched the develop- ment of a single butterfly, indeed, whoever shall but have compared an opened caterpillar with an opened moth, to him it will be evident that the fattv mass cannot be the liver. tf Chemical analysis has as yet contributed nothing towards the removal of the difficulties which still involve the different views upon this subject, although a careful investigation would most certainly settle the dispute. In ants* and r the cochineal insect fat has actually been found, and this consequently may certainly contribute to support the adoption of the opinion of this substance being found in all other insects. 11G. III. THE BLOOD VESSELS. We shall find the vascular system just as simple and uniform in insects as we have found their digestive apparatus complex. A vessel which passes along the back from the head to the anus constitutes the only blood vessel to be discovered in insects. That this canal is a true blood vessel, and indeed an artery, is proved by its regular contraction and expansion, which is very easily perceived exteriorly in transparent thin-skinned larvae. Malpighi, its discoverer, considered it as such, * Compare Gmelin, Handb. d. Theor. Chemic, vol. ii. Div. i. p. 469, No. 24, ;md p. 508. No. 1 ; 2nd Div. p. 1473, &c. 154 ANATOMY. and has described it as a great pulsating * vein. Subsequently to him, the other great entomotomists, Reaumur, Swammerdam, Bonnet, De Geer, have recognised the same organ, and concur with him in repre- senting it as a simple and wholly closed vessel. Even the very cautious Lyonnet can consider it as nothing else ; but he described the lobes of the dorsal vessel in greater detail, and has figured them more accurately than any of his predecessors. In recent times Cuvier, in his " Com- parative Anatomy," has repeated the descriptions of earlier anatomists, and even after this organ had been subjected to the most painfully patient investigations by Herold and Muller, its true structure has not yet been ascertained. Carus f at last discovered the motion of a fluid not only in the dorsal vessel but also in other parts of the body, and shortly after him Straus Durckheim recognised a structure of the dorsal vessel, which had been previously overlooked, which so entirely agrees with the insect type of organisation, that no doubt can be enter- tained of the correctness of his observation. My attention being drawn to it by Straus' communications, I made investigations upon the structure of the heart in several insects (for example, in the larva of Calosoma sycophanta, Lamia cedilis, Termes fatalis, &c.), and I have distinctly seen the valves and apertures mentioned by him. 117- According, therefore, to these most recent observations, the dorsal vessel (PI. XXII. f. 8 and 9.) is a thin canal composed of a delicate membrane, it is largest in the abdomen, and gradually decreases to- wards the head. In the abdomen it has on each side several apertures, as well as lateral muscular lobes, whereby it is attached to the back; where it enters the thorax it bends downwards (the same, f. 8. B.) that it may pass through the narrow, more deeply situated opening into its cavity, and then pursues its course above the oesophagus to the head, where it terminates with a small orifice. The number of the lateral apertures appears to vary (the same, a, a, a). Straus found eight in Melolonllia, I could observe but four on each side in the larva of Calo- soma. According to Midler's description of the heart there appears to * Compare his Dissert. Boinbyce. Lond. 1669, 4to. or his Collective Works, Lugd. Bat. 1687, 4to., vol. ii. p. 20. t Entdeckung eines cinfachen, vom Herzen aus bleschlcunigten Krcislaufes in den Larven netzfliiglichcr Insckten. Leipz. 1827. 4to. THE ORGANS OF DIGESTION. 155 be but one aperture in Phasma, which also has but one pair of lateral muscles. By means of these apertures the heart is divided into so many chambers, for behind each opening there are valves which separate the preceding space from that behind the opening, so that in Melo- lontha there are eight (PI. XXI. f. 1 8.) such consecutive chambers. The first, which lies close to the dorsal sheath of the last abdominal segment, is the smallest, and consists of one heart-shaped bag, which in front, towards the head, has an opening like a slit. The lips of this aperture consequently form the anterior side of the bag and close it, if blood, pressing forward from within, does not part them. The blood enters it through two small apertures, which likewise lie in front upon each side of the bag, but it cannot flow back through the same openings, for a half-moon-shaped valve which is affixed within the cavity of the bag beneath the aperture closes upon it, and thus, when the heart con- tracts, the blood must necessarily pass through the anterior opening. This first and most posterior chamber of the heart is succeeded by another in front, formed very similarly, but longer and more cylindrical, and which has also an aperture behind, viz. the anterior one of the first chamber. It is through this that the blood passes from the first cham- ber to the second when the heart contracts, and upon its dilatation blood pours into the chambers through the two lateral anterior open- ings. Thus, therefore, each chamber is always provided with blood, for the blood streams from one chamber to the other, beginning at the posterior, when that which has been received through the lateral open- ings from the cavity of the abdomen passes on by their successive con- tractions. We will explain how this contraction (systole) and dilata- tion (diastole ) of the heart take place after we have said a few words upon its structure. 118. According to Straus, two membranes are observed in the heart, the- exterior of which is smooth, dense, and longitudinally fibrous, conse- quently muscular. It is this which forms the above-described valves, for at the two margins of each lateral aperture it bends inwards. The posterior return forms the inner valve of that opening, and the anterior return the partition of the chamber, or both the anterior ones form the lips of the anterior opening. Both valves, as well as the entire internal lining of the heart, are covered with a transversely folded and looser 150 ANATOMY. layer of muscle, which is still thicker and stronger in the middle of each chamber. Perhaps both membranes are but the different layers of one muscular membrane, and then we might, by the analogy of all blood-vessels, entertain the idea of the presence of an innermost struc- tureless mucous membrane, which escapes observation by its delicacy. It is from the presence of these muscular layers that it is possible for the heart to contract and dilate. By both membranes simultaneously contracting the heart becomes straitened, and this distends again as soon as the membranes become flaccid after the contraction,, when the muscles of the lobes contract themselves. 119. To the posterior portion of the dorsal vessel which we find provided with apertures and valves, and which we must consider as the true heart, several triangular, flat, membranous muscles are affixed, the points of which pass on to a dorsal plate of the abdomen, and there attach themselves (PI. XXII. f. 9). If these wings (fliigel) of the heart, as they are called, are short, or consequently of the shape of an equilateral triangle, other muscles of the form of a band originate at the apex of this triangle, and pass in a diverging direction from each other, and insert themselves upon the abdominal plate, where this becomes membranous (Lamia (Ecl'dis}. Generally, however, the wings are so long as not to require the muscles of attachment (Melolontha, &c.), and they then take the shape of a very acute triangle. The conjunction of these muscular wings with the heart, which they merely retain in its place, is very intimate, without its being possible to say where ; whether it be by fibres passing from these wings into those of the heart, or whether the membrane of the heart sends forth lateral folds it is impossible to say. They lie in a row upon the two opposite sides of the heart, precisely where the anterior aperture of each cham- ber is found. They pass over these apertures, the fibres attaching themselves to a small membranous arch which crosses these orifices transversely ; consequently, in front of each orifice, there is a small semicircular hole in these wings, which are thus prevented from inter- rupting the flow of blood. These wings are wanting to the dorsal vessel of the Libellula, and Phasma has but one pairin the sixth abdominal segment. Besides this we find a pair of muscles passing from the posterior margin of the THE ORGANS OF DIGESTION. 157 heart, their apex being attached to the last abdominal segment and the colon, which has not yet been observed in other insects *. 120. The anterior portion of the dorsal vessel which passes through the thorax to the head, and which is not furnished with apertures and muscles (PI. XXII. f. 8. c), may be called the aorta if we call the pos- terior portion the heart. The part which may be considered as such commences where the dorsal vessel bends near the thorax to pass into its cavity, for from here the apertures and muscles are wanting. This bend is greater or smaller, according to the size of the posterior par- tition of the thorax, largest doubtlessly in the petiolated Hymenoptera or the Diptera, whose thoracic cavity is entirely separated from the abdominal cavity by the metaphragma. When the aorta arrives in the cavity of the thorax its course becomes then direct as far as the head, constantly keeping the central line, and accompanying the here straight oesophagus or stomach, and frequently united to it by a cellular mem- brane or the fatty substance. \Yhen there is a free and moveable pro- thorax it passes likewise into this through the common opening, or more rarely (as in Gryllotalpa f) through a small aperture in the meso- phragma (PI. XI. No. I. f. 7- a], and here still accompanies the oeso- phagus as far as the head. Here, close to where the oesophagus bends down to the mouth, consequently behind the cerebrum, the aorta sud- denly ceases with a somewhat distended orifice, without previously sending forth any smaller vessel ; in other instances it divides in a fork, each branch of which bends laterally, and terminates after a very short course likewise with a free orifice; or, lastly, we find three short, equal, radiating branches, each open at the extremity (for example, in Gri/l- lus hieroglyphicus, Klug. J). 121. We thus conclude the description of the blood-vessels of insects. The most laborious and patient endeavours of Entomotomists to discover other vessels remained unrewarded, until Joh. Miiller discovered a union of the ovaries with the aorta . We shall treat in greater detail of this * Cornp. J. Miiller, iiber das Ruckengefass, in Nova Acta. Med. Nat. Car. vol. xii. pars ii. pp. 576 and 586. f Ibid. p. 596. * Joh. Miiller, ib. p. 613. Ib. p. 613. 158 ANATOMY. connection lower down, in the Chapter where we speak of the sexual organs ; but we must defer hinting at their hypothetical use, as well as of the doctrine of a circulating system in insects, until the following division, to which we consequently refer. 122. IV. OF THE ORGANS OF RESPIRATION. We shall find the respiratory organs of insects as complex and per- fectly developed, as we have found their blood-vessels simple and imperfect. The relations between these systems appear to be in them completely reversed, for the air-vessels intersect the insect body as multitudinously as we find the blood-vessels do in the superior animals. We cannot here show whence this transposition of the usual relations proceeds, nor how an entirely different structure can produce a similar result, this belongs to Physiology ; we are here required merely to explain the structure and distribution of the air-vessels, and their external orifices. Our subject thence divides itself into two portions ; the first of which treats of the exterior organs attached to the respira- tory organs ; and in the second, we shall describe the internal air- vessels themselves. 123. A. Exterior Organs of Respiration. The exterior organs of respiration which are found upon the surface of the body, are of a triple character, namely, SPIRACLES, AIR TUBES, and BRANCHI^:. The first are easily distinguished from the last, by the presence of an orifice that opens directly into the tracheae, whereas the branchiae are membranous leaves, throughout which tracheae are dispersed, without opening anywhere. I. The SPIRACLES (spiracula, stigmata), which are the most fre- quently found of all the exterior organs of respiration, appear as incisions or small round openings at the sides of the segments of the body, which are sometimes surrounded by a peculiar oval horny ring ; or are encircled by merely the usual integument of the body, without any apparent distinction. Both kinds of structure are supplied with a muscular apparatus which opens and closes the aperture, so that the insect can either open it to receive air, or close it against it. We shall proceed with a description of their various forms, after this short indi- cation of their differences. THE ORGANS OP RESPIRATION. 159 Some which are never free, but lie concealed beneath portions of the horny integument, have no exterior horny ring, but a double-lipped incision, the lips of which are formed by a thickened margin fringed with short hair. This structure is very apparent in the large spiracle which lies in the uniting membrane of the pro- and mesothorax, and parti- cularly in Gryllotalpa (PI. XI., No. 1, f. 2, a. .), where, by reason of its length, it is very distinct. The horny lips are connected at their corners by a kind of joint, but in Gryllotalpa the lower corner of this incision, which lies near the anterior coxae, is broader and more prominent ; and the corner of the exterior lip projects beyond the opposite interior one, form- ing a kind of covering, thus preventing the influx of improper substances. The entire spiracle is closed by means of a small muscle, which, origin- ating from an inner horny projection of the lower corner of the lip, inserts itself in two horny half-rings, which surround the commence- ment of the tracheae. The orifice is opened or shut by the contraction or dilatation of this muscle. Other spiracles, which besides the lips possess an oval horny margin, present a somewhat more complicated structure. The horny ridge (PI. XXIII, f. 1 3,a,) is no distinct part, but merely the raised edge of the integument surrounding the spiracle ; it thus forms an exterior ring, to which the lips of the incision are attached. These lips (the same b. 6.) stand at the base of the ring, and are frequently covered upon their external surface like it upon its internal circumference, with sculptured horny scales (Oryctes nasicornis). Where they meet they again form a small projecting margin which, as in the former kind of structure, is surrounded by a fringe of fine hair. The corners of the lips lie close to the inner margin of the exterior ring, so that the true opening, upon the lips being closed, appears as the diameter of the oval ring. The closing apparatus of these spiracles is very complicated. The ends of the incisions, namely, or the corners of both lips, are pro- longed inwardly into a point (the same, c. c.), to which two triangular horny plates are so attached, that one angle of the triangle with the projecting point, and the second with the opposite one of the other horny plate, form a joint, but the third remains free. From the last, as well from the sides of the triangle which are applied to each other, a flat muscle originates (the same, e.) which, when it contracts, brings the free points of both triangles together, but those which stand in connec- tion with the inner points of the corners of the lips, it separates from each other ; thus is the incision closed : but when the muscle again 160 AXATOMY. relaxes, it re-opens. We must observe, at the same time, that a bag- shaped expansion of the tracheae originates from the circumference of the spiracle, and narrows towards the latter, in a funnel shape. By means of the tracheae arising from the point of the funnel, the whole expansion is drawn backwards, so that the axis of the funnel stands obliquely to the axis of the tracheae ; upon the inner side of this funnel, or that part next to the ventral cavity, the just described apparatus for the closing of the spiracle lies (see PI. XXIII, f. 1 3). Such spiracles are found only upon free or slightly covered parts of the body, for example, under the elytra of many beetles. A third form of the spiracles is distinguished from the preceding by the want of lips. In very small and round spiracles, the opening is free (for example, in the Lamellicornia), or at most covered with short hair upon their inner margin, and the entrance into the tracheae is only rendered difficult by the obliquity of its axis to that of the spiracle. In larger oval spiracles, the margins are occupied with stronger plumose spines, or hairy tufts (PI. XXII. f. 10), and these resist extraneous substances still more forcibly. The air is purified through these as through a sieve, and all prejudicial substances are caught there. This structure is very distinct in the large spiracle of the first abdominal segment of the male Cicada, as well as in the dorsal spiracles of the water beetles *. The fourth and last form of the spiracles is that observed in the larvae of the Lamellicornia. In these the very minute spiracle appears at first view to take a circular shape, and upon closer inspection it is found to consist of a broad margin and a concentric middle space, which beneath breaks through the margin and connects itself with the surrounding integument. This margin, which is often ornamented with distinct sculpture (PL XXIII. f. 4. a, a,) Sprengel considered as a half moon-shaped opening, occasionally closed by a sieve, when the sculpture of the margin was cribriform, or by toothed processes, when the sculpture took that figure, opposite which the inner round plate lay and assisted to close it. Treviranus t opposes this view of it, and asserts that the spiracle is entirely closed, but that minute ramifications of tracheae are spread upon its internal superficies, and imbibe the air, * See Cams, Analekten zur Natunvisscnscli. Dresden, 1829. 8vo. P. 187. PI. I, f. 13. And Sprengel, Commentar. &c. Plate II, fig. 23; and Plate III, fig. 29. ) Das Organische Leben, nen dargestellt. Bremen, 1831. 8vo. Vol. I. p. 2.58. THK OKGANS OK HKSPIRATION. 101 as in the branchiae, through the plate of the spiracle. Buth were mis- taken, for these spiracles have likewise a central aperture, which leads directly into the stem of the tracheae. This orifice, which is a small transverse incision, lies in the central round plate (PI. XXIII. f. 4. c), and is very small in proportion to the entire spiracle, and may there- fore be easily overlooked ; but Kaulfuss, in his drawings to Sprengel's Treatise, has everywhere indicated them. The exterior margin is, however, by no means perforated, but merely covered with sculpture, just like the exterior oval horny ring. I consider this margin therefore as the pre-formation of the subsequent oval horny ring, the central plate, however, as the two lips of the here still smaller incision. Inter- nally the main stem of the trachea is observed to originate from the circumference of the aperture, a distinct proof that the incision is its orifice (PI. XXIII. f. 4., d.d.). 124. / After noticing the form of the spiracles, the next most important subject is their situation in the body, which is tolerably uniform in the several orders, but there are a few divarications from it, which we may here briefly indicate. In the CoJeoptera each segment of the body has a spiracle, or, to speak more correctly, upon the boundaries of every two segments we find one. The first, and generally the largest spiracle, is seated in the uniting membrane of the pro- and meso-thorax, more closely approaching the exterior and lower margin of the former, where it gene- rally remains when those two portions of the body are separated. The second spiracle lies in a very similar situation, namely, between the meso- and meta-thorax, but it is so concealed by the elytra that it can be discerned only upon very close investigation. It is then observed between the two horny plates which we called above (page 81) the anterior and posterior wings of the scapulas. In a state of repose the two plates lie closely together, and thereby completely cover this spi- racle; but upon the expansion of the wings during flight, when the body filled with air distends, this spiracle also quits its concealment, that it may, like the rest, allow air to flow in and out. The concealed situation of this spiracle explains how it has been overlooked, particu- larly as we observe none in the similarly named segment of the larvae. Straus first observed it, and has exhibited it in the cockchafer and in others. The third spiracle lies between the meta-thorax and the first M 162 ANATOMY. abdominal segment ; it is frequently minute and indistinct, but occa- sionally, as, for example, in the Capricorn beetles, it is very large, indeed larger than the first. The following spiracles, six or seven in number, lie always between every two of the successive abdominal segments, so that the two last segments alone have no spiracles; we thus obtain ten spiracles upon each side, twenty together, a typical number which is never exceeded, but often also not attained. In the Orthoptera the spiracles are not differently situated. The first which is in the connecting membrane between the pro and meso-thorax is very large, particularly so in Gryllotalpa (PI. XI. No. I. f. 2. a, a); the second, between the lower wing of the scapula and the dorsal piece is here quite free and uncovered (the same, fig. 8. /i). The third spiracle, which properly should lie between the meta-thorax and the first segment of the abdomen, approaches more closely to the latter, and lies in Gryllus, F. (Acri/dium, Lat.) in a half moon-shaped hollow, which upon one side is partly closed by the projecting cover-shaped margin. All the succeeding ones are placed in a similar situation, namely, at the lower margin of each dorsal plate of the abdomen. In the B/attaria, on the contrary, the spiracles are always placed in the connecting membrane between two segments, and precisely where the dorsal and ventral plates meet ; the same is the case in Forjlcula ; in these also the third spiracle lies at the anterior edge of the dorsal plate of the first segment of the abdomen, where it is very distinct although but small. In the Hemipfera, which, by the structure of their thorax, approach closely to the Orthoptera, the first spiracle likewise lies in the connect- ing membrane between the pro- and meso-thorax ; it is tolerably large, and narrow, and is only apparent upon the removal of the pro-thorax. A second spiracle is found between the meso- and meta-thorax, and resembles the former in being a rather long, half moon-shaped, or straight incision, and is covered by a posterior projection of the margin of the meso-sternum. This spiracle consequently cannot be seen from the exterior from the preceding projection (PI. XIII. No. 5. fig. 2. /3) lying over it, and above it is concealed by the elytra. The succeeding spiracles are in these insects, as in the Ortlioptera, more approximate to the ventral segments, a spiracle being placed in each abdominal seg- ment, whereas by analogy it should lie between every two segments. In the male Cicada the first is very large, free, and always beset with strong setae at the margin, the following are smaller and indistinct. THE ORGANS OP RESPIRATION. ItvJ Kirby and Spence describe large lateral spiracles in the bugs, lying between the meso- and meta-thorax, but I could perceive in our bugs (Pentatoma rujipes and P. hce,morrlioidalis) depressions only at these parts ; but if the acute posterior margin of the prosternum, which lies precisely in this cavity, be removed, the spiracle is observed very dis- tinctly beneath it. In Belostoma a very distinct spiracle is found at the posterior margin of the pleura, consequently between the meta- thorax and the abdomen, which, however, appears to belong to the first abdominal segment, because in the bugs the spiracles lie always in the ventral segments themselves, and, indeed, at the exterior margin of the ventral plates, and not, as in the beetles, beneath the wings and the elytra. The Neuroptera alone, of the remaining orders, have a distinctly separated pro-thorax; it is here therefore that we must notice them. Semblis displays two distinct pairs (PL XIV. No. 3. f. 2. 4. a and /3,) of spiracles in the thorax, the first between the pro- and meso-thorax, and the second between the meso- and meta-thorax. Whether there be a third pair between the meta-thorax and the abdomen I could not clearly perceive either here or in Myrmecoleon, but in the dry speci- mens examined by me there appeared to be incisions. The two first pairs lie, also in the ant-lion, exactly in the same place. Panorpa dis- plays two pairs of spiracles in the thorax and five pairs in the abdo- men ; the two first lie between the pro- and meso-thorax, and between the latter and the meta-thorax, and display themselves as small brown points. In the abdomen they are placed, as in all Neuroptera, in the connecting membrane of each pair of segments, closely in front of that to which they belong. In the Dictyotoptera, as those most closely allied to the preceding order, with the exception of the Libellula? and Termites, they are, from their minuteness, difficult to investigate. The Libcllu/ce have two pairs of spiracles in the thorax, one pair being between the pro- and meso- thorax, each of which, however, is covered by a small scale originating at the posterior margin of the pronotum ; the second pair is seated between the meso- and meta-thorax, at the sides of the thorax. The former are long, somewhat bent incisions ; the latter very small, ovate, two-lipped spiracles. I have observed none between the meta-thorax and the abdomen. It has also been said that they have no abdominal spi- racles. But Reaumur and Sprengel admitted their existence in those M 2 164 ANATOMY. larvae which live constantly in water, but Kirby and Spence * again denied it, their attention being probably drawn to it by Roesel's f observation of their respiration through the anus. This intestinal respiration Suckow J has confirmed by showing branchiae in the colon, and thus proved the entire inutility of spiracles. But in the perfect insect there are seven pairs of spiracles upon the central abdominal segments, which are covered however by the margins of the dorsal plates lapping over them as they lie in the soft connecting membrane. In the Termites the spiracles are found in analogous situations, but those of the abdomen are so small that they are seen with difficulty. The remaining three orders very closely agree both in the structure of the thorax as well as in the situation of the spiracles. All possess our in the thorax, two of which are upon the limits of the pro-? thorax, between it and the meso- thorax, and the other two lie between the meso- and meta-thorax. In the Hymenoptera, in which the thorax consists of a hard horny case, and the segments are closely united together, the posterior pair of spiracles lie upon the meta-thorax itself, whereby they distinguish themselves from all the other orders ; besides which the anterior pair of spiracles are covered by a small scale-shaped projection of the posterior margin of the pronotum, which scale (tegula, comp. 77-) li es precisely beneath the anterior wing, and is very readily recognisable in the wasps. In PI. XII. No. I. f. 1., wherein the thorax of Cinibcx is represented, the letters a and /3 point out the situa- tion of the spiracles, as also in the same plate, No. II. f. 2. in the thorax of a Scolia. The spiracles of the Lepidoptera are distinguished only by possessing a narrow, scarcely perceptible, horny ring, which lies con- cealed beneath the hair (PI. XIII. No. IV. f. 2. shows at a and /3, where they are placed.) In the Diptera they appear as short, some- what compressed tubes, particularly the first, between the pro- and meso-thorax, as is shown in PI. XIV. No. I. f. 2. in Tabanus, and No. II. f. 2. in Myopa. A similar uniformity exists in the situation of the spiracles of the abdomen, for they always lie in the connecting membrane of the segments, and are covered by the projecting margins of the dorsal plates. The numbers of the spiracles are thus shown in their situation. If * Introduction to Entomol., vol. iv. letter xxxviii. f Insectenbelustigungen, 2 band. Wasserinsecten der 2 classe, Taf. II. r.nd III. Reusing. Zeitschr. fur die Org. Physick. 2 band. 2 lift. S. 36, &c. PI. I. and II. THE ORGANS OF RESPIRATION. 165 we call to mind also the general law which makes the insect body to consist of thirteen segments, whereof one forms the head, three the thorax, and nine belong to the abdomen, the number of the spiracles is readily ascertained. The thirteen segments have namely twelve connecting membranes, of which the first only (between the head and pro-thorax) and the last are never supplied with spiracles, consequently there cannot be more than ten on each side at most. But as the number of the abdominal segments considerably varies, it consequently frequently happens that there are fewer spiracles. I have observed twenty in the water-beetles (Dyticvs)'. According to Degecr and La- treille *, the locusts and Lepidoptera display as many : the Lamelli- corniaand Cerambycina possess eighteen. Many Orthoptera, the Ter- mites, and Libellulce possess the same number. The Hymenoptera have but seven distinct abdominal segments, the last of which, according to the general rule, bears no spiracle ; in general they possess sixteen : Panorpa has fourteen ; many Diptera still fewer, as but five or six distinct abdominal segments are perceived in them. 125. II. The AIR TUBES are absolutely nothing but elongated spiracles, although they are not always found, where the spiracles are placed. They are only observed in insects which live in the water, namely, in the larvae of many Diptera and some water-bugs (Nepa, Rannlra}, and are placed either at the first or the last abdominal segment. They here appear as either long or short horny tubes, which pass directly from the general integument of the body, being open at the end, and within the orifice they are surrounded by simple or plumose setae, or else entirely unprovided with them. The larva of the common gnat (Culex, PI. III. f. 3) is very gene- rally known as possessing this organ, which is placed obliquely at the last abdominal segment. Simple branches of the tracheae pass into this tube, opening where it terminates. The end of the tube is surrounded by setae, and these support the animal upon the sur- face of the water when it places itself there to breathe. In the pupa state the tube at the end of the abdomen disappears, and instead of it two bent tubes project from the thorax between the pro- and meso- * P. A. Latreille sur quelqucs Appendices du Thorax dcs divers lusectes. In Mem. du Museum d'Hist. Nutmvllc, turn. vii. 166 ANATOMY. thorax (PI III. f. 4). The majority of the larvae of the genera most closely allied to this gnat possess no such air tube, hut true branchiae or gills, yet the larvae of Citironomus* have likewise two conical air tubes upon the anal segment (PI. III. f. 5) ; besides which they are easily distinguished by a more elongate vermiform shape t, as well as by their blood red colour, from the true larvae of the Culicidcc. A similar structure is found in the larvae of Stratiomys ; in them the entire last segment of the abdomen is elongated into a tube, and at the aperture of the tube it is provided with a wreath of plumose hairs placed in the form of a star. This coronet, which is much larger than that of the larva of Culex, likewise supports the much larger creature upon the surface of the water when it goes thither for fresh air ; and it likewise takes air bubbles, which are inclosed by the setae, down with it to the bottom of the stagnant pools which it inhabits, as a provision for its next inspiration j. The larvae of the genus Eristalis display a considerably longer anal air tube ; in these also the last joint is extended into a membranous tube, in which a second narrower and corneous one is contained, which at its open end is provided with a similar crown of hair. It is into this tube that the two branches of the tracheae pass after having united into one. The thick, white, cylin- drical larva which lives in the mud of pools, in sewers, and in excre- ment, directs this tube to the surface of the water, which hangs there by means of the above-mentioned setae, while it itself lies tranquilly at the bottom, or else continues feeding. If the water should rise, for example, after rain, it lengthens this tail by pushing the inner tube as far out as is requisite. This elongation can be extended to several inches, whereby the length of the tail exceeds several times that of the body. For the expiration of the air thus received two other very short air tubes are placed upon the first segment of the body, directly behind the head ; the anterior ends of the above described main stem of the tracheae pass into these after having previously, as well as the posterior ends, become united by means of a transverse branch. We also observe anal air tubes in the genera Nepa and Ranatra, but which are distinguished from those above described in the first place by * The larvae have gills (branchiae), as I have recently observed (Author, MS. Note). f These larva were formerly considered as a genus of annelides, and were called Branchiurus. See Oken's Zoologie, 1 band. s. 383. Taf. 9., and Viviani Phosphor. Maris, :;. is, n. * See Swammerdammj Biblia Natuiw, I'l. XXXIX. f. 1 ;',. THE ORGANS OP RESPIRATION. 167 their number, two always being present, and secondly by their form, they being simple horny tubes unprovided with setae at their end. In Ranatra they are as long as the body, and in Nepa half its length. It seems to be a very general law, that the situation of the spiracles should be at the posterior end of the body, not only in the Diptera, but also in all larvae which live in water and are unprovided with branchiae. With respect to the larvae of the Diptera, those yet investigated have their spiracles in that situation: for example, the flies and (Estridce. The larvae of the water-beetles likewise (for example, Dyticus and Hydrophilus) have their spiracles at the anal end, contiguous to the anus, and have none at their sides, although Sprengel describes and even figures them there *. 120. III. GILLS, or BRANCHIAE. This third description of the organs of respiration is particularly distinguished from both the others by its want of apertures to admit the air into the tracheae. The gills are processes of the epidermis in the form of hair or leaves, in which delicate tracheae ramify in every direction. These vessels imbibe the air mixed up mechanically with the water, and conduct it to the main stems concealed in the body, by means of the branches of which it passes to all the internal organs. Through this arrangement insects pro- vided with gills do not require atmospheric air, they consequently do not rise to the surface of the water, but live constantly in it concealed among water plants. The branchiae may be separated into two divisions, by their forms; the one being delicate and slender, resembling hair, while the other is broad, thin, and lamelliform. The hair-shaped branchiae seldom appear singly, but generally in approximate fasciculi, which are formed by either the ramifications of one or of several main stems (PI. III. f. 6.), or by filaments radiating from one point (the same, f. 10). The epidermis of these processes is exceedingly delicate, as well as the small silvery tracheae enclosed by it. This kind of branchiae is the most usual and general ; it is found particularly in the larvae and pupae of the gnats. The lamellate branchiae are found only in the Dictyotoptera and the Neuroptera, and appear as broad or pointed lanceolate leaves, and are found on each side of each abdominal segment, or only at its end. * CoinmcnUu-., {.. ','>!. N... xx. PI. II. f. '20. 168 ANATOMY. Several, or at least two leaves, are found at each place, so that each segment of the body has never less than four branchial leaves. They are generally uniform, but an instance is known (Ephemera Jusco-grisea, De Geer*,) in which one of the branchiae is lamellate and the other is a fasciculus of filiform ones. If we look to the orders in which branchiae are found, we shall speedily see that they are not rare, and, indeed, that the majority of larvae which live in water breathe by means of gills. The following are the genera whose larvae thus respire : Among the Culeoptera we find hairy branchiae in the larvae of the whirlwigs (Gyrinus t), which rise from the sides of each segment, and clothe the body as simple, tolerably stiff, hairy processes. The closely allied Dyticus have no gills, but spiracles, which lie contiguous to the anus ; the larva of Hydrophilus piceus likewise breathes through spiracles thus placed, but the larva of Hydrophilus Caraboides, has, according to Roesel's figure +, ramose branchial fasciculi on each abdo- minal segment. The Orthoptera never live in water either as larvae or as perfect insects, they have consequently only spiracles as the exterior organs of respiration. Many of the Hemiptera, both in their larva and perfect state, live in water, but branchiae have never yet been observed in them. Both young and old, when they wish to breathe, come to the surface of the water, and receive air through the spiracles. Nepa and Ranatra have air tubes, which we have mentioned above. Whereas in the orders of the Dictyotoptera and Neuroptera the branchial apparatus is very general. In the first of these orders, the larvae of the Ephemera and Libellulce live constantly in the water, and have branchiae. In the larvae of the Ephemerae, they lie at the sides of the body, four upon each segment, and they consist of small leaves of various forms. In Ep.fusco-grisea one branchia is a leaf, and the other a fasciculus ; in Ep. vulgata both are leaves, very narrow, and clothed at the margin with long fine hairs. The branchiae of the larvae of the LibellulcB are not placed at the sides of the abdominal segments, but upon or within the last segment ; and in Agrion they form three large * De Geer, M^moires sur les Insectes, vol. ii. part ii. p. '29. PL XVIII. t'. '.'>. f Ib , vol. iv. PI. XIII. f. 1C 19. J Inscctenbelustignngen, vol. ii. Vv';is>cr-Int. Klassc, p. 3'2. Fl. IV. DC Gccr, ih. PL XVI. f. ;5. THE ORGANS OF RESPIRATION. 169 clavate leaves fringed at the margin. The larvae of JEschna and Libel- lula breathe through fasciculated branchiae, which lie in the colon. Thither proceed the terminal ends of the four main stems of the tracheae ; they transpierce the membrane of the colon, and hang as thick fasciculi within the cavity of this organ *. As the creature imbibes water by means of it, and thus again rejects it, it helps to assist it in swimming, which, without this auxiliary aid, it would find it difficult to effect, from its deficiency of other swimming leaves. Other larvae swim by means of the branchial leaves, which move with an incessant alternating vibration. Among the Neuroptera we are acquainted with the families of the Phryganodea and the Semblodea, whose larvae inhabit water. Both breathe during this state only through branchiae,, which in the former consist of two leaves placed on each side of each abdominal segment, but varying in form according to the genera, but in the latter they appear as simple or plumose, tolerably long processes, which consist of several joints, becoming gradually acuminate, upon the under surface of which the tracheae ramify, protected by two rows of setae f. Branchiae seem very general in the family of the gnats, among the Diptera, as they are found not only in the larvae but also in the pupae. This is the case in the genus Chironomus, whose larvae described above breathe through exterior tubes, but whose pupae are furnished with two radiating fasciculi of branchiae at the thorax (PI. III. f. 6.). These branchial fasciculi are seated close to the spot where later the first spiracle of the thorax is found, namely, between the pro- and meso-thorax. The same is the case in the genus Simulia ; the former has air tubes at the anal end as well as at the thorax, the latter two large branchial fasciculi between the pro- and meso-thorax (PI. III. f. 9 and 10 |). The reversed relations obtain in the genus Anopheles, whose larva, described as a remarkable water animal, first by Goeze , and afterwards by Lichtenstein ||, but which G. Fischer IF ascertained to be the larva of this gnat, bears hairy branchiae at its anal end, but whose pupa is provided * Suckow in Heusing., vol. ii. part i. p. 55, &c. PL I. and II. t Ib., p. 27. PI. III. f. 24. t Compare Thon's Archiv. der Entomologie, vol. ii. no. ii. PI. II. Beschaftigungen der Berliner Gesellsch. Naturfors. Freunde, vol. i. p. 359. PI. VIII. || Wiledeniann's Archiv. fur Zoologie und Zootomie, vol. i. No. i. p. 108. PI. III. 5f G. Fischer, Sur quclqucs Diptcres de Russie. PI. I. f. 1 16'. 170 ANATOMY. with two curved air tubes between the pro- and mesc-thorax (PL III. f. 7 and 8.) Among the Lepidoptera but one caterpillar, that of Botys stratio- talis has been observed to possess branchiae *. In this they consist of delicate small hairs which clothe the whole body, but particularly laterally, in the vicinity of the future spiracles, they stand in fasciculi. The tracheae are observed in them as glittering silver-white threads. The caterpillar lives constantly in the water upon the leaves of Stra- tiotes aloides. I have myself observed a very similar caterpillar of a moth upon Ceratophyllum demersum, but I was not successful in breeding it. Doubtlessly others also exist among the allied genera and species, but which have hitherto escaped detection. It must strike as remarkable, that among the Lepidoptera, which apparently, from the great development of their organs of flight, are destined to dwell in the air, larvae should be found which select a place of residence of such a very opposite nature, whereas among the Hymenoptera, which appear more adapted to dwell in a variety of media, no single instance should occur of one having been observed, either in its larva or perfect state, to live in water. It is indeed true that some of their larvae live in moist places, such as the parasitic larvae of the Ichneumons, but branchiae have never yet been detected in them. 127- B. INTERNAL ORGANS OF RESPIRATION. The internal organs of respiration are the most simple and most uniform parts found in the insect body ; for they universally present themselves as ramose tubes originating from the spiracle, the exterior air tube, or from the root of a branchia, and thence spread to all the other organs. Malpighi, who by his dissection of the silk-worm was the first to obtain a correct insight into the internal structure of insects, was also the first discoverer of these internal organs ; pre- viously it was thought that insects did not breathe, an opinion which was originally propounded by Aristotle, and subsequently generally received. As to the structure of these tubes serving for the function of respira- tion, and which have been called AIR TUBES or TRACHEA, we shall find * DeGccr, vol. i. jart iii. PL XXXVII. f. .3 and 6. THE INTERNAL ORGANS OF RESPIRATION. 171 that they consist of three distinct layers, which, taking them from the exterior, appear in the following form : The outermost membrane (PL XXII. f. 11.) is transparent, very smooth, without being perceptibly librous, but hard, and generally colourless. Coloured tracheae, which we now and then observe, for example, brown in Locusta viridissima, red in Phasma gjgfis, or black, as in the larvae of Dyticus and Hydrophilus, derive their colour from this exterior skin, whereas both the others, especially the second, are constantly of a silvery white, and shining. A dark colour facilitates very much the detection and unravelment of the extremely delicate tracheae, particularly when they run upon the clear ground of other organs. But in those cases where the tracheae are not coloured their investigation is not very difficult when freshly killed individuals are selected for the purpose, for in them the tracheae are still filled with air : they then display themselves as silvery white, glittering threads, which here and there appeardull and transparent, from moisture having at those parts already penetrated them. In general, the last and most delicate ends are still filled with air, which, however, is forced out when the creature has been long immersed in spirits of wine, and it then becomes difficult to obtain a satisfactory view of their distribution. The exterior membrane of the tracheae consequently is structureless, nor is it in very close connexion with the second, but loosely surrounds it, leaving everywhere a free space between them, which is quickly perceived upon a microscopic investigation, and thereby readily con- vinces us of the presence of at least two layers. The second layer consists of a single, tense, elastic, and very delicate filament, which twines spirally around the innermost membrane, so that its windings are everywhere, or at least very generally contiguous. This thread appears to be simple and round, but which is occasionally difficult to ascertain from its delicacy, but the microscope displays how it distributes itself about the circumference of the vessel, and that it scarcely leaves the smallest space between its successive windings, and which is filled only by membrane. In some instances, for example, in Locusta viridissima, and indeed in all insects provided with large tracheal stems, the filament becomes broader, resembling a band, and can be distinctly distinguished as such. Sprengel * detected in such larger tracheae ramose filaments, or perfectly closed rings, which were * Commcutar. tie Par!., &c PL II. f. 14. 172 ANATO3IV. separated by broader membranous spaces, these he has figured as round in Cetonia aurata * : in Lamia lextor he even saw small spots between the windings, whereby the vessels of this insect appeared punctate. When an air-vessel sends off a branch the space between the two successive convolutions then widens, and the branch com- mences with its own spiral filament (PL XXII. f. 11), whereas that of the stem continues uninterruptedly; but if a trachea divides into two equal branches, each begins with its own new spiral filament, and that of the stem terminates at the point of division. These spiral filaments of the tracheae may be considered as analogous to the cartilaginous rings in the windpipe of the superior animals, although these are sepa- rated from each other, and connected only by their softer parts. But this fibrous layer of the muscular membrane in the vessels has the same function, for the contraction of the spiral filament straitens the tracheae, and thus helps to promote expiration, whilst its succeeding expansion facilitates the inspiration by opening a larger space in the vessel for the admission of air. The cartilaginous rings of the wind- pipes of the superior animals fully accomplish this last purpose, and they thereby distinguish themselves from the tracheae of insects. The innermost third membrane, which Lyonnet, Marcel de Serres, and Straus-Durckheim admit, but Sprengel denies, is, according to the investigations of the former, a smooth, transparent, delicate, mucous membrane, and, as it were, a continuation of the exterior epidermis, with which it also stands in connexion at the orifice of the spiracles. The spiral filament lies closely adhesive to it, so that upon a rupture of the vessel its remains hang affixed to the detached spiral thread, whence Sprengel prefers considering it as a connecting membrane be- tween the spiral fibres rather than as a distinct layer. But the fact of this innermost membrane peeling off when caterpillars moult, or pass from the larva to the pupa state, and that in place of it a new one is formed beneath, speaks distinctly in favour of its being considered as a peculiar and a separate one. This anatomical structure of the air-vessels is found precisely the same in all the orders, and although their form is subject to many varia- tions, yet their structure but very seldom participates in this difference. This participation of the structure in the difference of form is main- tained by Straus and Marcel de Serres to be found in the air bags of the * ConniicnUir. dc Pad. PI. II. f. 19. THE INTERNAL ORGANS OF RESPIRATION. 173 Lamellicornia, in which, according to these entomotomists, the spiral filament is deficient, whereas others, particularly Suckow and Sprengel, assert that they exist, of which we shall speak in detail below. 128. With respect to the differences of form in the tracheae, according to Marcel de Serres they may be divided into three main groups, which that writer thus distinguishes : 1. ARTERIAL AIR-VESSELS. They originate directly from the spiracle, and ramify with the most delicate branches from this simple stem to all the internal organs. 2. TUBULAR or PULMONARY AIR-VESSELS. They do not receive the air directly, but stand in connexion with the spiracle by means of the former. They are larger than the arterial air-vessels, their course is more regular and straight, their diameter broader, and their branches, on the contrary, smaller. 3. VESICULAR AIR-VESSELS. They are of two kinds, either large bladders, in which the air collects, and whence the branches spring, or small bladders in the branches themselves, and frequently the terminal distended ends of the branches ; both forms are never found together. Upon inspecting first the arterial air-vessels, as those most generally found, but little that is extraordinary is to be remarked in them ; each main stem originates from the internal margin of each spiracle with a broader base, which narrows somewhat after a short course. Here also is the point of division of the main stem ; next a branch spreads for- wards and backwards, which passes to the anterior and posterior spiracles to unite with each main stem originating from them. By means of these arches all the stems of the tracheae stand in close connexion together. Between these two communicating tracheae the remaining ramose branches originate, and each spreads more particularly to those organs which lie most approximate to it. These branches frequently open into each other, and form stems running contiguously to the intestinal canal, the muscles, and the sexual organs, and whence the delicate branches for these organs originate. The number of the branches originating from a main stem, with the exception of the two connecting tubes, is indeed very variable, but we may assume that more branches spread from the tracheae of the thorax than from those of the abdomen. This arises from the greater number of organs existing in the thorax, particularly the number of muscles, 174 ANATOMY. whereas in the abdomen there are many spiracles, but proportionally fewer internal parts. The vessels of the thorax consequently belong more to the organs of motion, and those of the abdomen to the intes- tinal canal and the sexual organs. Two of the many branches which the main stem of the first thoracic spiracle sends off always go to the head. One runs superficially over and contiguous to the mandibulary muscles, and also unites to its oppo- nent upon the opposite side (Melolontha) , and distributes itself with its branches to all the superior internal portions of the head. From it the ring encompassing the eye proceeds, or, where this is wanting, the branches which spread in the pigment of the eye. The inferior branch accompanies the nervous cord and the oesophagus into the head, and distributes itself to the lower lying muscles, the maxillae, and the labium. A third branch, which descends downwards anteriorly, or as in the Mantodea, two equal branches spreading in this direction pass into each anterior leg, and each distributes itself with innumerable ra- mifications to its very point. The extreme posterior branch is the one connecting it with the second thoracic spiracle, the remainder origin- ating between this and the beforementioned one, distribute themselves to the muscles, and several pass into the meso-thorax. The spiracle between the meso- and meta-thorax, generally the smallest, has also the fewest branches, namely, besides the connecting ones which unite it to the first and third spiracle, it has a main branch for the middle leg, and several ramifications for muscles. From the third spiracle between the meta-thorax and the abdomen it is generally that the greatest number of branches originate, namely, the two connecting branches, the branches for the third pair of legs, and several large ones to the muscles. The spiracles of the abdomen have each their two connecting branches, and besides which several ramifications for the internal organs. The number of these branches differs much in the genera and families, but they are about the same from the several spiracles. In the Mantodea they unite to a second, more internal, common duct, and from which the branches for the internal organs originate *. In all caterpillars, maggots, and in the larvae of the Hymenoptera we observe only arterial vessels, the same in all the predaceous and swimming beetles, and in the Heteromera and Tetramera. In all other o * * Marcel de Serres, Mem. du Museum, vol. iv. PI. XVI. f. 1. THE INTERNAL ORGANS OF RKSPIRATION. 175 insects we find them in conjunction with pulmonary and vesicular vessels, but the terminal ramifications, as well as the secondary ones, are of the arterial description. 129. Tubular air vessels are chiefly peculiar to such larvee as are provided either only at one end or at both ends of the body with spiracles ; besides which the communicating tubes of the stems of the spiracles are tubular. Under the name of TUBULAR we understand such air- vessels which proceed uninterruptedly from one end of the body to the other, and which only send forth here and there small accessory branches ; or else the simple communicating vessels between two ap- proximate spiracles, and which are without any accessory ramifications. Both have this in common, that they preeminently extend according to the longitudinal axis of the body, whereas the arterial air-vessels take their course in an opposite direction to this longitudinal course. Whence it becomes apparent that the tubular air-vessels are never insu- lated, but can only exist in conjunction with the arterial; the former are, as it were, the main stems and the latter their twigs. We will now describe in greater detail some of the chief tubular air- vessels. With respect to their first form we may assume that all larvae which live in water possess more or less developed tubular main stems. Among the Coleoptera this is the case in the larvae of Dylicus and HydropTiilus. The yellowish green larvae, figured by Roesel * of the large water-beetles (JDyticus marginalis, d'nni- diatus, &c.), have two large spiracles at the apex of the last abdo- minal segment, exteriorly contiguous to the short, plumose, anal apex. Two large, broad, black tracheae originate from them, which ascend undivided as far as the first thoracic segment, the future prothorax. There each furcates, and then both branches run to the head, one spreading over the muscle of the mandible and the other beneath it. Two small accessory branches of these two main stems spring from it at the commencement of each abdominal segment, but the inner one of these two is considerably the largest in the fourth, tenth, and eleventh segments, for these three pass to the intestinal canal, the anterior one to the stomach, the posterior ones to the ilium and thick * Insectenbelustiguugen, torn. ii. Wasseriiisekten der Ersten Klasse, p. 8. PI. 1 f. 2-7. 17f> ANATOMY. gut, whereas all the rest are branches which run off to the muscles. But, on the contrary, the two exterior branches in the second segment exceed the inner ones in size, turn upwards to the back of the seg- ment, and here anastomose, whereby is formed one transverse commu- nicating passage between the two main stems. All the transverse accessory branches are here arterial, but the large main canal which runs longitudinally in the insect is tubular. We find a similar dispo- sition and structure, in all the essential portions, in the tracheal system of the larva of Hydrophilus piceus, as is evident from Suckow's figures*. Tubular air-vessels are very general among the Orthoptera, where likewise, as is always the case, they are connected with arterial branches, or even with vesicular vessels. The tracheal system of Mantis oratorio described and figured by Marcel de Serres may serve us for an example f. Two narrow vessels originate from each of the seven abdominal segments, the shorter exterior ones of which unite in a direct tubular vessel, which runs beneath the margin of the abdomen, and passes on to the third spiracle of the thorax. The inner somewhat longer vessels unite in arches, forming a second longitudinal tube, which proceeds in an undulating line close to the superior wall of the intestinal canal, and also passes into the thorax. A third tubular vessel comes out of the thorax, running very closely to the intestinal canal : it also takes an undulating course, but beneath that organ, and sends forth branches laterally, Avhich again unite in a fourth direct tubular vessel, and which is connected at its anterior and posterior extremities with the first named one, which runs at the edge of the abdomen. All these tubular vessels give off but few branches, and it is only from the central lower longitudinal tube that some delicate branches are given off to the intestine, and it is from the central inner small vessel, originating at the spiracle, that the air tubes come for the sexual organs. The air-vessels of the larvae of the Libellulce are also tubular, and are very uniform in their distribution with those of the larvae of the beetles which live in water. Two large main stems, serpentine at the dorsal portion of the intestinal canal, which, after being bound by the ' In Heusinger Zeitschr. vol. ii. No. i. PL IV. f. 26. See a detailed description in H. M. Gaede Dissert. Sistens. Observation, qucsd. dc Insector. Vcrmuniqiie Structure. Chilon, 1817. 4to. t M<;m. du Museum, torn. iv. PL XVI. f. 1. THE INTERNAL ORGANS OF RESPIRATION. 177 colon, from which they originate in a tuft, take their course to the head, where they again furcate. On each side of the ventral portion two smaller vessels lie, which are united to the dorsal vessels by means of transverse branches. The upper one of these runs also to the head, the lower one, taking its course nearly in the centre of the body, termi- nates on the contrary in delicate ramifications * at the stomach. We find also in the perfect insect both the ventral and dorsal stems, the latter communicating by means of delicate canals with the seven spi- racles of the abdomen. The tubular vessels, lastly, are found very generally in the larvae of the Diptera. The larva of the common gnat (Cw/e.r) has two large dorsal stems, which originate, already divided, from the above described posterior air tube, and give off their fine branches to the internal organs t. In the larva of Eristalis tenax, Meig., which has been called the rat-tailed maggot, from its long air tube (PL II. f. 8.), both the two great tracheal stems unite, previously to their passing into the inner tube of the air tube, by means of a transverse branch, and remain for a small space separated, lying convoluted in front of the internal aper- ture of the tube, but it is only where they pass into the inner tube that they are truly united together. In the body itself they are never again united, but in the first segment in the membranous head there is ano- ther connecting tube which proceeds directly behind the cerebrum. In front of this connection they become considerably narrower, but behind it each stem proceeds out of the head as a fine tube passing into a small air tube placed at each side of the head, which were necessary for the expiration of the previously inspired air. It is probable that such anterior air tubes are found also in the larvae of other Diptera. A similar structure is found in the larvae of all the flies ; but they want the tail, and both the tracheal stems separately vent themselves at the posterior obtuse surface of the body (PI. II. f. 1.). The larvae of the Hi/menoptera have also tubular main stems, but which, as they are formed of small tubes that proceed from the spi- racles, are never so large and developed. Two main stems consequently proceed on each side of the body, united in each segment by means of a transverse connecting vessel, but there orginate from them, at those places where the tubes of the spiracles pass into them, innumerable * Suckow in Heusinger, f. 7. & 9. f Swammerdam Bib. Natuno, PI. XXXVII. f. 5. h. 178 ANATOMY. ramose or arterial vessels, so that the tubular main stem is less insu- lated *. Precisely the same structure is exhibited in the larvae of the Lepidoptera, but the peculiar tubular structure is still more indistinct, for in general the transverse connecting tubes are also wanting. 130. The vesicular air vessels are properly only distended tubes, or the distended ends of accessory branches, it is thence that they are never found alone, but they are always in conjunction with arterial or tubular air vessels. They also appear under two chief forms, for they are either very large bladders, lying chiefly in the abdomen, whence arterial air vessels originate, or they are the vesicular distensions of the branches of arterial air vessels themselves. The first form of the vesicular air vessels is found in the Hymen- optera, Diptera, Cicada, and in a somewhat altered figure in many grasshoppers. In the Diptera, at least in the true flies ( Muscidte) the Syrphodea and the (Estridce, two large air bladders have been observed at the base of the abdomen, contiguous to the intestinal canal, which are tolerably uniform in structure with the large tubular vessels, but the twistings of the thickish spiral filament are wider apart, the filament itself divides here and there, and is interrupted at other parts, whence the entire surface does not appear so regularly transversely striated as in the tubular vessels (PI. XXII. f. 12., membrane of the air bladder of Musca vomitoria). Their form is regulated by that of the abdomen, so that they are often ovate or very generally vertically compressed, and are here and there angular, in consequence of constrictions. A large trachea originates from their under surface ; it runs forward and backward to the head and anus, and gives off lateral tracheae to the spiracles of the thorax and abdomen. Other finer vessels run over the superior surface of the bladder, and ramify to the internal organs. Whether they originate from the bladder itself or from the connect- ing vessels lying beneath it I could not perceive distinctly in flies, but it is the case in Scolia and in Apis according to Leon Dufour. But this whole air bladder is nothing else than the tubular vessel of the larva, which during the pupa state has shortened and distended, and of which we took notice in the preceding paragraph ; this air bladder must * Compare Swanimerdam Biblia Natune, PI. XXIV. f. 1. in Apis Mellijica. THE INTERNAL ORGANS OF RESPIRATION. 179 consequently be found in all flies whose larvae breathed through the tail itself, or through spiracles seated there. The presence of this air bladder explains the cause of the glassy perfectly transparent abdomen of so many Diptera, for example, of Volucella pellucens, Meig. The Asili, which have a longer, narrower, more extended abdomen, possess, according to Marcel de Serres *, several small and successive vesicles, for example, Asilus barbarus has sixty on each side. Many Hymenoptera display a similar structure. In some species of Bombus I have found precisely the same air bladders at the commence- ment of the abdomen, as has also Leon Dufour in Scolia f. Carus | has described them in the large Cicada. The air bladder originates within the circumference of the large spiracle which lies between the thorax and abdomen, it distends a little anteriorly, but spreads especially backwards, where it extends to the sixth or seventh segment ; before impregnation, whilst the ovaria and testes are still filled with their contents, they are limited to a smaller space, but after copulation they occupy almost the whole abdomen, particularly in the males, in which they are generally larger in compass, doubtlessly in connection with the vocal organ, which in the females is merely indi- cated. Hence is explained the opinion of the ancients, who held that the males were empty. In the grasshoppers the bladders have a somewhat different connec- tion with the rest of the respiratory system ; and they also vary con- siderably in form from the former, for in these they consist of bags of a somewhat longish oval shape, very pointed at both ends. In Locusla viridissima two such bags originate at each spiracle, they thence ascend close to the inner side of the general integument up to the back, where they attach themselves to a flat horny arch, which originates from each ventral plate projecting into the cavity of the abdomen, and which is affixed to the ventral plate only at its commencement. Each of these arches supports two air bladders, which, however, do not pro- ceed from one but from two separate spiracles, so that they altogether form a zigzag line. But they are connected also above and below by a narrow longitudinal tube, and from the lower ones there are vessels connecting them with the opposite ones of the other side, and from the upper ones originate the branches which are distributed to the internal . de Mus., as above, p. 362. f Journal de Physique, Sept. 1830. J Analekten zur Naturwissenschaft und Heilkunde. Dresden, 1828. page 158. fig. 1517,9. N2 180 ANATOMY. organs. Thus, therefore, the air bladders of the abdomen form a com- pact net-Avork, which is, as it were, spread out between the spiracles and the horny arches. If the abdomen be drawn together by muscular contraction the horny arches rise, extend the tracheae longitudinally, and consequently the air contained within them is forced out ; but upon its expansion the air again streams in, when every bladder, through the elasticity of its filament, is again shortened and dis- tended. The respiratory system of Truxalis nasutus, of which Marcel de Serres has given a figure *, is still more complicated, for in it the bladders do not originate immediately from the spiracles, but, by means of long tubes, from the common tubular vessels which connect all the spiracles, and at the opposite end unite in a second but more delicate longitudinal tube. Also the two oppo- site bladders are held in connection together by undivided tolerably narrow tubes. In the abdomen there are twenty bladders, ten on each side ; in the thorax six larger ones, four in the meso- and meta- thorax, one very large pear-shaped one above, at the dorsal portion of the pro-thorax, close to the crop, and besides many vesicular disten- sions of the arterial vessels ; in the head there are six large bladders, two laterally, contiguous to the muscles of the mandibles, two above, at the vertex over the eyes, two in the forehead before the eyes, and between these several smaller vesicles. The second chief form of the vesicular air vessels is found among the Coleoptera in the family of the Lamellicornia, among the Lepidoptera in the Crepuscularia, particularly in the males, and then in the dragon flies. In the Lamellicornia the chief distribution of the air vessels, as throughout the Coleoptera, is arterial, for fascicles of air vessels ori- ginate from each spiracle; but each finer branch distends, prior to its ultimate and finest ramification, into an oval bladder, which is of a more delicate structure than the rest of the branch, whence Marcel de Serres and Straus deny the presence of the spiral fibre in these vessels, which Suckow maintains to be the case. It is true that these bladders are more transparent than the tubes, but they exhibit a peculiar punctured structure, as was even perceived and figured by Swammerdam f, and also by Sprengel J ; and thence I would assume * As above, PI. XV. ; i t Biblia Nature, PI. XXIX. f. 10. J Commentar., PI. I. f. 1113, THE ORGANS OF GENERATION 181 that in these bladders, as in the larger ones of the flies, the spiral fila- ment has torn from the distension, and only the rudiments of it are present in the darker places. These bladders accompany all the intes tines, pass everywhere between the muscles, and are particularly accu- mulated superficially beneath the integument. A precise description is consequently impossible, from the manifold reticulation of the branches, and a single glance at the masterly representation of it in Straus will explain it better than any words unaccompanied by figures could possibly do, we therefore refer to his anatomy of Melolontha. The vesicular distensions in the tracheae of the Libellulce are found chiefly in the thorax, and in it they lie exteriorly, contiguous to and between the muscles. They are generally pyriform, whereas those of the Lamellicornia and Lepidoptera are perfectly oval ; the bags also appear to me to be connected by tracheae and to form distinct lacings. Among the Lepidoptera we find the bladders chiefly in the male Sphinges and Phalente, and are sometimes small and sometimes large, as in Acherontia Atropos, Ochs. They are of a coarser structure than those of the beetles, so that the presence of the spiral fibre is here subject to no doubt. According to a figure in Sprengel the membrane of the bladder has sometimes a cellular appearance, and this might then be considered as an approximation to the structure in the Lamelli- cornia. SECOND CHAPTER. OF THE ORGANS OF GENERATION. 131. THE second chief system of the vegetative organs comprises the sexual organs destined to the propagation of the species. Under this name we understand both the vesicular and the tubular parts which lie in the abdomen generally affixed at one end, which, in a variety of forms and connections are united together in main stems, and open in one evacuating duct at the end of the abdomen beneath the anus. This last definition is subject to no exception in true insects, for what has * Commentar., PI. III. fig. 24. 182 ANATOMY. been considered as exterior sexual organs and sexual apertures at the base of the abdomen in the male Libellula are by no means such parts, as we shall have an opportunity of proving below ; in them also that aperture is found at the end of the abdomen, in the vicinity of the anus. These vesicular and tubular organs consist, like the intestinal canal, of several divisions, which, as the general character and function of the sexual organs consist in the secretion of fluids, may be distinguished as proper secreting organs (testes and ovaria), conducting organs for the secreted fluids (vasa deferentia and oviductus), repositories for the secreted fluids (vesica seminalis and uterus), and as evacuating organs of the secreted material (ductus ejaculatorius and vagina). These main divisions are found in function, although frequently but little distin- guished in form and figure from each other, in all the internal sexual organs, as will be shown in the course of our investigation. This sketch consequently comprises the most general structure of these organs, and it will therefore be merely the individual, generic, family, and ordinal differences which will occupy us in the course of our inves- tigation ; but we will previously say something about their anatomical structure. 132. The determination of the structural relations of the membranes of the sexual organs is subject to many difficulties, in consequence of the delicacy and minuteness of these parts- It is only in those divisions which possess a greater extension that it has been possible to distin- guish the presence of two layers of membrane. The exterior of these two membranes is coarser, firmer, and of a muscular consistency ; the internal one, on the contrary, is more delicate, transparent, simple, and corresponds with the internal mucous tunic of the intestinal canal or the exterior epidermis. The presence of both the membranes in the large vesicles is subject to no doubt ; they can there be readily and securely exhibited ; even in the more delicate evacuating ducts of the secerning organs they are distinguished by the difference of their con- sistence, which in the internal one is considerably less than in the external one. It is more difficult to prove their presence in the secerning organs themselves, but J. Miiller * has shown them, at least in the * Nova Act* Phys. Med. XII. 2. PL LV. THK ORGANS OF GENERATION. 183 ovaries : but it still remains doubtful whether the glandular testes consist of these two layers, which, however, may be assumed, from the similar structure of analogous parts. 133. The preceding observations apply with equal force to all sexual organs. But if we contemplate their general form we shall imme- diately meet with varieties which do not admit of any further generali- sation, and this circumstance compels us in this place to examine more closely the differences of form which the sexual organs severally present. Propagation is, like life in general, the result of two agents acting reciprocally upon each other. In the lowest forms of organisation, where such a separation of the animating activities shows itself less perceptibly, the propagating agents themselves cannot either appear separately, we consequently there find simple germs susceptible of development. By degrees an ACTIVE and a PASSIVE agent are pro- duced, both of which are found at first in the same individual (snails), but they soon separate into two distinct individuals, and thereby constitute the essential character of such individuals. In the former, luxuriant energy, universal momentum, and a continual impulse towards the appeasement of internal urgent desires ; in the latter, patient sufferance, quiet reserve, a tarrying for excitement, and an ultimate satisfaction in the discovery, of the deficient unknown some- thing. The former character is called the MALE, and the latter the FEMALE. But where shall we find the differences of these two characters more distinctly expressed than in the multiform insect world ? The above cited distinction is here found so strongly marked 'that its high significance can no longer be subjected to doubt. We shall return to this subject in our physiological chapter, and it is there only that it will find its true place ; we can merely indicate it here to enable us to arrive at the primary difference of the sexual organs. This we have now found, we have thus become acquainted with two kinds, and have distinguished them as MALE and FEMALE. 134. The differences of the organs of generation of both therefore lie based deeply in the conditions of life. We necessarily ask, how does it become evident to us ? Anatomically investigated, the character of the female is the formation of the germs, that of the male secretion of sperm ; 184 ANATOMY. all organs, therefore, which display germs (eggs) are female, and all which prepare spermatic moisture must be called male. The female sexual organs of insects consequently display bags full of eggs, ovaria; the male, sperm-secreting vessels or glands ; from both originate the above characterised closer or more distant evacuating ducts, which are pretty uniform in both sexes. We may consequently distinguish in both female and male organs different divisions, which are, however, connected together, and which must necessarily constitute the different divisions of our description of the sexual organs. 135. I. OP THE FEMALE ORGANS OF GENERATION. The female sexual organs (genitalia feminina) of insects consist of internal and external ones; the internal ones of OVARIES, the OVIDUCT, the UTERUS, other peculiar appendages, and the VAGINA ; the exterior ones of the ORIFICE OF THE VAGINA, and its appendages, as the ACULEUS, the VAGINA TUBIFORMIS, and the VAGINA BIVALVIS. It is not always that all the above named parts are present together, either one or several are wanting, the ovaries are deficient only in barren, undeveloped females (the neuter bees, &c.), but the evacuating ducts never ; all other appendages may, on the contrary, disappear. A. INTERNAL SEXUAL ORGANS. 136. THE OVARIES. The ovaries are tubes or bags in which the eggs are secreted from the formative substance of the creature, and where they remain until their impregnation. We always find in insects two such organs of similar structure in the same individual ; they are so placed that one lies on each side of the intestinal canal, generally filling the lateral space in the abdomen. In colour they are generally yellow, but in form they are subject to many varieties, which, however, may be classed under the following divisions : I. The ovaries are simple bags, in which the germs of the eggs ar contained. This primary form, which is the most simple of all, is subjected to no subordinate differences *. * The ovarium saccatum described by J. M'uller in Nova Acta Phys. Med., torn, xii, p. 612. does not belong here, but will be classed below, with the ovarium furcatum. FEiMALE ORGANS OF GENERATION. 185 Such ovaries are found in Ephemera and Stratiomys. Muller calls this form bunches of ovaries (ovaria racemosa *), and supposes that the exterior., tunic of the bag, or properly the bag itself, is wanting, the eggs being connected together by means of air-vessels ; but Swammerdam's figure misled him f. In a female of Ephemera marginata, Fab., De Geer, which I dissected, I clearly observed the exterior tunic, the ova were contained within it, egg being linked to egg by a delicate filament. In Stratiomys also Swammerdam has dis- tinctly represented the bag]:}:. II. The short ovaries, which contain but few germs, are placed longitudinally upon a large, bag-shaped, common ovarium. There are many subordinate_differences of this peculiar form, which we will briefly indicate. 1. OVARIA PECTINATA (PL XXVII. f. 2.) are short egg tubes, which contain but few germs, and are placed in a row upon the upper side of a common duct ( Mantodea). 2. OVARIA ECHINATA, common egg ducts, long, broad, wider ante- riorly and suddenly pointed, having beneath many very small scale- shaped egg tubes, which lie over each other (dragon flies). 3. OVARIA IMBRICATA (PL XXVII. f. 8.). The whole upper sur- face, with the exception of a narrow edge upon the lower margin, is covered with short tile-shaped egg-tubes, which lie upon each other, and embrace the intestine like a roof. Each tube contains a large developed egg and behind it the minute germs of two or three others (grasshoppers, crickets, Phryganea, Sialis, Tipula, Sirex, &c.). 4. OVARIA BACCATA. The common ovarium is a bladder or tube upon the entire upper surface of which are placed the short egg-tubes, generally containing but few eggs, (Coleoptera vesicifica, each tube with from one to four eggs; Semblis, each with six to nine eggs). 5. OVARIA DICHOTOMA (PL XXVII. f. 5. ovaria fur cata, Muller). The common ovarium is forked, and upon each prong, and particularly upon their opposite sides, there are many tubes, containing but few (3) egg germs (Gryllotalpa). 6. OVARIA RAMOSA (PL XXVII. f. 6.). The common egg duct does not simply furcate, but several branches are given off one after the other, each of which contains some egg germs (Lepisma). * Nova Acta Phys. Med. p. 601. 11. f Bib. Naturae, PI. XXV. f. 1. Ib.Pl. XL VIII. f. 1. 186 ANATOMY. III. Long tubular ovaries, which contain many egg germs, are col- lected together at one part of the common duct. These tubes are either entirely free, and distinctly separated from each other throughout their whole course, or else united together by a loose cellular tissue (for ex- ample, in Harpalus ruficornis). 1. OVARIUM SPIRALE (PI. XXVII. f. 10). There is but one egg- tube to each ovarium, but which is very long, and it is twisted spirally from its apex to its base ; a rare form, which has been observed only in Sarcophaga carnaria and some other kinds of flies. 2. OVARIA FURCATA (PI. XXVII. f. 7- Ovaria saccota, Miill.). There are but two short ovaria, containing indistinct egg germs, and which unite with the common duct by means of a fork; at the point of union there is a bag (uterus) in which the egg germs pass through their changes until the pupa state (Diptera pupipara *). In Polistes also there are but two egg-tubes, each of which however contains several eggs. 3. OVARIA DIGITATA (PL XXVII. f. 8 and 9). A few, from THREE to FIVE, such egg-tubes hang at one spot of the common duct. Many Lepidoptera (for example, Liparis Mori, with FOUR tubes, each of which contains about sixty eggs), particularly the smaller ones (for example, Tinea, likewise with FOUR tubes, each of which contains about twenty-five eggs; and Ptcrophorus, with THREE tubes, each containing about twelve eggs) ; and the Hymenoptera, (for example, Chrysis, with THREE tubes, each with three eggs; the same in Xylo- copa ; in Anthidium, also THREE tubes, each with about eight eggs). In Nepa, Pediculus, and Psocus there are FIVE tubes, each in the latter genera containing five eggs. 4. OVARIA VERTICILLATA (PI. XXVII. f. 11). Many very long tubes originate at one spot, upon the very short common egg duct. They run upwards in a long filiform point. Such ovaria are found in the majority of female insects, namely, in most Lepidoptera, many Hymenoptera, and almost all Coleoplera. Miiller's ovaria conjuncta are but a trifling variety of this form, the superior filament hanging more closely together, and forming an inter- twisted cord. The fertility of the species regulates the number of the egg-tubes and their turgidity. Oryctes nasicornis, Melolontha, Cetonia, * Leon Dufour in the Annales des Scienr. Nat. torn. vi. p. 299, &c. According to him the ovaria contain merely a whitish mass, but no distinct egg germs. FEMALE ORGANS OF GENERATION. 187 and Notonecta have six tubes, each with from five to six eggs ; Veapa vulgaris and Silpha atrata seven tubes ; Tenebrio, Leptura, Saperda, Blatta, Ascalaphus, Bombiis terrestris, from seven to ten tubes, each with from four to six eggs ; Cicindela, Carabus, Dyticus, Staphylinus, Hydrophilus, Cerambyx, Lamia tristis from ten to fifteen tubes ; Bu- prestis mariana twenty ; Blaps mortisaga thirty, each with four eggs ; Apis mellifica above a hundred, each with seventeen eggs. 5. OVARIA CAPITATA (PI. XXVII. f. 12). They merely differ from the preceding in their short tubes not running upwards in a point, but which distend into a large knob, whence the point proceeds as a thin filament (Lucanus). 137- The situation of these very various ovaria is nearly the same in all insects, for they always lie laterally in the abdomen contiguous to the intestinal canal, and fill the whole remaining space of the abdominal cavity not occupied by that organ. They often lie free and separated from each other, but sometimes fold over from both sides towards each other, and thus form a covering over the nutrimental canal, containing it between them. The latter then forces itself into the anterior portion of the thus formed longitudinal canal, runs within it, and posteriorly it again presents itself, passing over the common duct, which the colon always covers above. Such approximate ovaria are connected by the tracheae, which approach them with their large stems, and then accom- pany each of their individual tubes by delicate accessory branches to their very extremity. There is still another means for retaining the ovaria in their place, which is their communicating duct with the dorsal vessel, discovered and described by Joh. Muller *. Each indi- vidual egg-tube, or occasionally the common egg bag, extends in a thin, very delicate, but tolerably firm filament, which ascends anteriorly and above to the dorsal vessel to discharge itself therein. This connexion invariably takes place at that portion of the organ which we have described as the aorta, sometimes at a great distance from the ovarium, for example, in the thorax. This kind of connexion is peculiar to the ovaries of the third chief division, for the connecting filaments of each egg-tube unite in a cord, or frequently, prior to their connexion with the dorsal vessel, they meet and form a single short tube, for example, " Nova Acta Phys. Med. n. c. vol. xii. part ii, page 555, &c. 188 ANATOMY. in Carabus*. The connecting filaments of the egg-tubes of the second class remain, at least frequently, separated, and discharge themselves singly into the aorta f. It yet remains undiscovered how the connexion is formed with the vesicular ovaries, but it is probable that a single duct passes from the end of the bag to the artery. We shall treat of the use of this connecting duct, which Miiller has so admirably represented, in our physiological division, where we speak of the development of the eggs. . 138. THE OVIDUCT. The OVIDUCTUS, or tuba ovarii, is that portion of the evacuating duct of eggs which extends from the ovarium to the connexion of the two ova- ries in the common evacuating duct. It is a delicate long or short tube, sometimes thin and filiform, or broader and vesicular, and when so it has a thicker muscular structure (Semblis). It is rarely that each oviduct is supplied with peculiar glandular appendages which secrete a gluten to spread over the eggs, by means of which they are glued together. In Hydropkilus, which has four such appendages attached to each side of the oviduct, they are filamentary, gradually decreasing, blind canals, and have a granulated glandular appearance, and are doubtlessly glands, and most probably secrete the material from which the female prepares the glutinous mass enclosing the eggs ; but where such ap- pendages are wanting this takes place in the vagina, or in the duct com- mon to both ovaries, which is then supplied with peculiar appendages for this purpose. In general the oviduct is longer in small ovaries which contain but few egg germs, shorter, on the contrary, in larger ones rich in germs ; but their dimensions are regulated by the age of the insect ; long ducts are found in young individuals, and they become shorter in older ones which are ready for impregnation, or already impregnated. 139. That portion of the duct of the ovaries which extends from the union of the tubes to the orifice of the spermatheca is called the egg- canal. It is generally of greater compass than the oviduct, and distends into a belly in the middle, forming a convenient cavity for the reception of the eggs. But no other object attends this reception * Nova Ada Phys. Med. n. c. PL LI. f. 3. f !*> pl - L - f - 2 - FEMALE ORGANS OP GENERATION. 189 than their mere passage, for the impregnation of the egg, as we shall see below ( 208), does not take place here, but probably at the end of the egg-tube, at least its development commences there. In those instances only in which this portion of the female organs is provided with appendages which secrete a gluten do the eggs remain somewhat lonsrer in this common duct to be covered by the secretion of those O * glands, that they may be thereby fixed as with a gum to the leaves of plants and other objects. Consequently this portion of the sexual organ is nothing more than a canal, and we must ascribe as well to insects as to many other inferior animals a uterus bicornis ; indeed in the majority of cases, particularly those which possess ovaries having many egg-tubes, a uterus multicornis, for at the end of the egg- tube the development of the egg commences, and here consequently also its impregnation by the semen ensues. 140. APPENDAGES TO THE EGG-CANAL. The egg-duct is most rarely a simple organ unprovided with vesicular or vascular auxiliary cavities, as, for example, in Donacia, Erisialis tenax, Musca, Tipula, Ephemera (PI. XXVII. f. 13) ; in the majority of insects, on the contrary, it exhibits various appendages which take a variety of forms, and exercise different functions. These appendages vary in number from one to five. If one only be present it is always a vesicular or purse-shaped distension of the duct, which appears destined to the reception of the male semen during copu- lation, and is thence called the SPERMATHECA. This organ is always- situated at the superior parietes of the duct, and opens into it with a small orifice surrounded by a callous margin. This margin is properly the sphincter of the neck of the bag, which prevents the escape of the semen. When it opens the semen flows immediately into the duct from the mere situation of the bag. According to Audouin, the male organ during copulation passes into the orifice of this bag, and thus pours the semen directly into this receptacle. We find this kind of simple vesicular appendage in Acheta, Blatta, Anthidium (PI. XXVII. f. 14.), Ascalaphus, Sialis, Semblis, Psocus, and Nepa ; the same in Hydrophilus, Tenebrio, Lytta, and Chrysis, but in the latter it has a superior or lateral vascular apex (PI. XXVII. f. 15.), which is evi- dently the organ we shall presently describe as the gluten gland. In general, namely, this vessel discharges itself into the duct contiguously 190 ANATOMY. to the spermatheca, yet in the instances named above not, but into the spermatheca itself. It is somewhat similar in Psocus, for here the gluten vessel does not merely discharge itself into the spermatheca, but lies entirely in it. For thus I interpret the purse-shaped appendage found by Nitzsch * in Ps.pulsatorius, in which from one to four pedi- culated knobs are enclosed which unite into one duct, which runs into the excretory duct of the spermatheca. If TWO appendages are found at the duct it must be carefully observed whether they are symmetrical in situation and form or not. Two dissimilar appendages are found in most insects, (namely, the genera Carabus, Harpalus, Melolontha, Lucanus, Meloe, Spondyla, Sirex, Apis, Xylocopa, Tinea, Pterophorus, and Cercopis}. The one is larger and broader than the other, purse-shaped, and corresponds both in situation and function with the just described spermatheca. In Melolontha (PI. XXVII. f. 16. ), Lucanus, Spondyla, and Cer- copis it is a short-necked pear-shaped bladder; in Pterophorus the same, but a short blind bag springs from it laterally ; in Xylocopa (PI. XXVII. f. 17- ). Apis, and Tinea it has a longer very narrow neck ; in Trichius a superior vascular appendage; in Sirex (PI. XXVII. f. 18. a), in which it is very large, at the part where the bladder con- tracts into a neck, two tolerably long, pointed appendages are found ; in Meloe it is constricted near the middle, and the lower smaller half has a round auxiliary bladder, which discharges itself into it by a nar- row canal. The second appendage (PL XXVII. f. 16 18. &.) is in general much longer, but also thinner and vascular. This form itself, which is common to all the secreting organs of insects, bespeaks its glandular function. Observation has also taught us that a white glutinous liquid is secreted in this organ, which, after the eggs are laid, disappears. This gluten likewise covers the impregnated eggs, and it is very pro- bably what fastens them together, as well as to other objects ; conse- quently all appendages which are not spermathecae are called gluten glands or vessels. With respect to their form, besides the simple, tubular, and vascular form which are found in Trichius, Tinea, and Cercopis, there is a clavate one found in Melolontha, and a vesi- cular one furnished with a short neck in Meloe. In Xylocopa it is a long gradually decreasing bag, which discharges itself by a very Compare Otrmar's Magaz. vol. iv. p. 281. PL II. f. 3. e. f. fig. 4 and 5. FEMALE ORGANS OF GENERATION. 101 narrow tubular pedicle into the uterus ; in Harpalus and Spondyla, on the contrary, it is a round bladder, which has a very long, twisted, fine duct, and which in Spondyla contains a hard horny interior ; in Ptero- phorus the vessel distends before its orifice into an ovate bladder ; and in Lucanus (PI. XXVIII. f. 1. b, b) ^there are two such bladders, which unite by means of tivo short ducts into a common one, and originate from very fine, short, twisted vessels, by their distension. The form of these organs, lastly, is very peculiar in Elater murinus, in which, according to Leon Dufour, they are vessels successively furcat- ing, which at the base of each fork distend into a triangular bag. The symmetrical appendages in Hippobosca resemble these, but the bag- shaped distensions are wanting. Where the duct has two symmetrical appendages, as in Lepisma (PI. XXVIII. f. 3.), Musca, and Pediculus they are always gluten depositories; in Lepisma they are large and bag-shaped, and upon the upper surface here and there constricted ; in Musca longer and clavate ; but in Pediculus, on the contrary, they are two short blind bags, provided with accessory points. We find three appendages in Gryllotalpa, Calosoma, and Stra- tiomys. In the first instances two of them are equal, namely, clavate or vesicular gluten vessels, which empty themselves into the duct by means of narrow canals ; the third, on the contrary, is the bag-shaped spermatheca, which in Gryllotalpa has another superior, long, vascular appendage. In Siratiomys Swammerdamm * found three long, vascular, gluten ducts, which originated from round gland- ular bodies. Four appendages are seen in some Lepidoptera, for example, Pontia Brassicce. The most anterior one is a simple, tolerably long, twisted vessel, which in others ( Gastrophaga Pini, see further below) consists of two furcate branches ; the second is the spermatheca ; the following are again long twisted vessels, which unite in a short duct after they have previously distended in two oval bladders. In Cicada, Latr. (Tetti- gonia, Fab.), in which there are also four appendages, two symmetrical vessels are found in front of the spermatheca, but the vessel behind it is simple but much longer than the two first. Five appendages, lastly, are found in several, particularly the Nociuce. A bladder-shaped, one-sided, sometimes long and clavate, or distended * Bib. Natura, PL XLII. f. 8. 192 ANATOMY. and egg or pear-shaped one, which discharges itself into the duct by a narrow canal, is the spermatheca; the other four are vascular gluten glands. In Fanessa Urtlcce they are short, the anterior one broader than the posterior, both discharge themselves into the duct at one part but at opposite sides, before the spermatheca ; in Gastrophaga Pini (PI. XXVIII. f. 4.) they are very long, and the anterior as well as the posterior unite into a simple but very short canal. The anterior one, which discharges itself close in front of the spermatheca, is distended in the middle into a bladder ; in the posterior ones, which discharge themselves into the vagina, this vesicular distension takes place at the end of each single tube before they unite into a common duct. The poison vessels of the Hymenoptera aculeata are appendages of a peculiar description. In them a round, perfectly ovate bladder (PL XXVIII. f. 5, 6. b, 6), with a narrow duct, discharges itself into the sting, which we shall describe below ( 145). This bladder lies quite at the end of the abdomen close to the orifice of the sexual organs. It contains a bright clear fluid which is secreted by two either long very fine, much twisted vessels, or of shorter ones, originating from a fasci- culus of furcate vessels (Pompilus*}, which opposite the orifice sink into the bladder, and either separated as far as their orifice, as in Vespa crebro (PL XXVIII. f. 6. a, ), or as in Apis mellifica (f. 5. a, a), are united into one vessel, a little distance before the connexion with the bladder. May not the posterior vessels of the Lepidoptera, which we have just described, be analogous to these, and both be pro- perly considered as organs secreting urine ? 141. THE VAGINA. The last portion of the common evacuating duct lying behind the egg-evacuating duct is called the VAGINA. It is a short direct tube, narrower than the egg canal but wider than the oviduct. Its function being to receive the penis of the male and to assist in depositing the eggs, it is, like all the other organs of insects which require constant distension, held in this state by horny leaves and ridges. There are generally three such horny plates, one above, one lateral, and one be- neath. In Harpalus the superior plate is a thin bone, which towards the exterior distends in the shape of a shovel, and is there armed with * Ramdohr, Verdauungsorgane, PI. XIV. f. 5, FEMALE ORGANS OF GENERATION. 193 strong thorns; in the Capricorn beetles (Cerambycina) it is elongated into a horny, many-jointed ovipositor. In Hydropkilus it runs out on each side into a horny point, which Suckow * considers as the analogue of the clitoris. In Melolontha the vagina has on each side a small pocket, into which the lateral wings of the penis pass during co- pulation, which explains the cause of the protracted union of this insect. In all insects provided with an aculeus or an ovipositor, the vagina opens at its base, so that its canal passes directly into that of the ovi- positor. The valves and spines of this apparatus are consequently nothing more than the horny bone which lies within the vagina, and which is then prolonged beyond it. B. EXTERNAL SEXUAL ORGANS. 142. The external sexual organs of insects do not always project beyond the apex of the abdomen, but usually lie in the cavity into which the orifice of the anus and of the vagina open. This cavity, common to both, is formed of two valves, the one larger, lying upon the dorsal side, and the other smaller, upon the ventral side, and beyond which the former projects all round. These two valves, which are not visible exteriorly, but are enclosed by the dorsal and ventral plates of the last abdominal segment, are evidently nothing but the last segment itself, those called the last being the last but one. It is only thus that we can explain the disappearance of the segments of the larva in the perfect in- sect, in which we shall also generally discover nine segments if we include the last concealed one. But where there are nine visible segments the last is not then concealed, but free. It is within this last abdominal segment, whether it be concealed or free, that the orifice of the vagina is found, and indeed, beneath the anus, divided from it only by a projecting plate. The entrance itself is opened, mostly by horny substances, which have partly been described in the preceding paragraph in the description of the vagina. The lateral horny ridges, namely, becdme more elongate, so that they project as far as the limits of the valves, gradually separating, and thus forming a spacious entrance. The length of the vagina depends upon that of these horny ridges ; they are short in the Carabodea, and often armed at their apex with a strong hook * Reusing. Zeitschr. vol. ii. p. 254. O 194 ANATOMY. palus rujicornis), which doubtlessly retains the penis during copulation. In the Capricorn beetles unprovided with an ovipositor (the Prionodea) they are long, superiorly broader, pointed towards the apex, and gently bending from each other. There are other forms in other insects. In the orders possessing an ovipositor they appear as its valves, or as its wings in those which possess only a vagina bivalvis, this leads us to the investigation of the free sexual organs which project beyond the apex of the abdomen. 143. The free, exteriorly visible, sexual organs of female insects are of a threefold description, at least three chief forms entomologists have dis- tinguished by peculiar names, namely, the LAYING TUBE (vagina tubi- formis), the LAYING SHEATH (vagina bivalvis), and the ACULEUS, called also the TEREBRA, but which is one and the same organ with the preceding. The LAYING TUBE (vagina tubiformis, PI. XXIV. f. 14.) is a mere continuation of the abdomen, and consists, like it, of rings which gra- dually decrease in compass, so that the largest and first, exactly as is the case in the telescope, receives within it all the rest, when this organ is withdrawn within the abdomen, wherein it lies concealed. These rings are nothing else than segments of the abdomen itself, which have adopted this altered shape and function in the course of the progressive alteration of the relations of organisation. The proof that this opinion is correct is shown in their number, for in the majority of cases (for example, in the flies,) there are nine abdominal segments, when these rings of the vagina are added to the visible ones of the abdomen. The anal aperture also lies in this tube, which could not be the case if it were merely an ovipositor. Thence, therefore, the last of these tubes only can interest us here, from its containing the female organs. In Cerambyx it is a leathery canal, of which that side nearest the venter is supported by two horny ridges ; at the end of each bone there is a short two-jointed process, the first joint of which is large, thick, bulb- ous, and armed on the exterior with short spines ; the second, however, is small and round, and has two stiff setae at its extremity. In the flies, which all possess a tubiform vagina, its last joint has above a horny plate, to which also two short single-jointed, hook-shaped, crooked processes hang attached. The tubiform vagina of the ruby tails (Chrysis) appears, as far as I have been able to ascertain from FEMALE ORGANS OP GENERATION. 195 dry specimens, to have precisely the same structure, only that in these, as well as in the flies, each ring has its horny covering, which are con- nected together by membranous parts. 144. The VAGINA BIVALVTS is most closely related to the vagina tuln- formis. It is found in the Orthoptera, some Neuroptera (Raphidia), and the Tipularia. In its most complete development it is a sabre- shaped tube, which curves upwards, into which the vagina opens, and it is formed of two valves (Locusta, PI. XXIV. f. 10 14.) I consider these two valves as the two lateral horny leaves mentioned above in the description of the orifice of the vagina, and which here are prolonged and now take the form of valves to that organ. The internal valves corresponding with the last abdominal segment become also visible, and here appear as the cover both above and below (f. 10. A, B,) at the base of the vagina bivalvis itself. All Orthoptera, consequently, have nine distinctly visible abdominal segments. In Locusta this vagina is long, sometimes indeed (Locus, viridissimd) even longer than the body, each valve is gently sloped, and has a channel upon it's exterior surface which projects internally as an elevated ridge. At the base it is covered beneath by the last deeply emarginate ventral segment, above it lies the anus, and contiguous to it two short, simple, spinous processes. Between the two larger valves there are two smaller ones (f. 12 and 14. b, i,) which are connected by a delicate membrane with the internal elevated ridge, and sometimes lse themselves in this or remain sepa- rated from it. Frequently the apex of the exterior vagina is split at the channel, when the exterior sheath appears, at least at its end, to consist of four pieces *. In Gryllus, instead of this projecting vagina we observe four short thick processes, the lower ones of which are moveable, and form one articulation with the superior ones that are closely attached to the abdominal cover. From the superior, stronger, thicker ones thus intimately connected two processes are continued within the abdomen, and to which are attached the muscles moving the lower ones ; the orifice of the vagina lies between the lower ones, and the anus above the superior ones. We may make the following * Kirby and Spencc, Introd. to Ent., vol. iv. p. 152., mention six pieces, but I have never observed in our indigenous Locusts any but the structure described above, and never six divided pieces. o 2 196 ANATOMY. comparison between this organ and that of Locusta, the lower moveable processes are analogous to the two valves of the vagina bivalvis, the superior ones however to the spinous processes contiguous to the anus, but with this difference, that in Locusta these processes are articulated to the horny piece which bears them, and which lies between the orifice of the vagina and the anus ; in Gryllus, on the contrary, the superior processes form an integral portion of that horny piece. Acheta agrees in structure with Locu.sta, but its vagina is more delicately constructed; the anal processes are longer, and at their apex apparently jointed. The female Tipula have likewise a bivalve vagina which very much agrees in structure with that of Gryllux. In Ctenopkora alrata, two pointed, long, and sabre-shaped processes originate above from the last dorsal plate, and bend from the sides towards each other, forming a bivalved vagina. They correspond to the superior immoveable processes of Gryllus or the moveable processes of Locusta. Beneath this last dorsal plate, and consequently between the valves, the anus is placed. A triangular fleshy process encompassed by a delicate horny margin separates it from the orifice of the vagina lying beneath it. It also has on each side two processes of the last ventral plate, which are above shorter, broader, inwardly arcuate, and gently bowed externally. These two valves form the true vagina, and therefore correspond to the inferior processes in Gryllus and the long vaginal valves in Locusla. In a state of repose they lie concealed between the superior or anal processes, and all four appear to form a bodkin-shaped process. 145. The TEREBRA, or ACULEUS, is found in all the Hymenoptera and in the Cicadaria. With respect to the aculeus of the Hymenoptera, although it has been occasionally tolerably well explained by the earliest entomologists, it has not always been recognised by modern ones, and therefore fre- quently imperfectly described. This fact is the more striking as it has actually nearly the same structure in its essential parts in all the families, and is merely subject to slight differences of form. For the present we will pass these over, and proceed to examine its essential parts. The chief character in which the terebra is distinguished from the vagina bivalvis is the presence of a second pointed boring organ lying between the valves. This fuller development of it is not found in the FEMALE OKGANS OF GENERATION. 197 vagina bivalvis, but it is indicated in the shorter internal valves, which in Locusta viridissima are united to the larger ones by membrane, but in other instances they are found free and separate. The terebra of the Tenthredos is an intermediate form ; it, consequently, does not pierce firm substances, but merely guides the eggs into already existing cavities ; but the aculeus forms the cavity itself for the egg, pierces into bodies not firmer than itself, and as a defensive instrument it wounds very severely. We may therefore distinguish the EXTERIOR SHEATH (vagina aculei) and the inner STING (aculeus, sen terebra) as the chief parts of this kind of ovipositor ; we will first turn our atten- tion to the sheath. We have but little to say of the exterior sheath, for its differences are unimportant. It always consists of two valves (PL XXIII. f. 6. a, ), which are united by articulation with the dorsal plate of the last abdominal segment, by which it is partially covered above ; the ventral plate then covers it from below. They are as long as the sting itself, and lying together form a tube, in which the latter is completely con- cealed. If the sting project beyond the apex of the abdomen they accompany it. A thus projecting sting (aculeus exsertus) Latreille calls a terebra. But when the sting lies concealed within the abdomen (as for example, in the bees,) the valves are there also, and they embrace the concealed sting (aculeus abscondilus) precisely in the same way as the exserted one. The exterior upper surface of the sheath is generally rough and uneven, particularly in the projecting aculeus, and entirely covered with short hair; the edges are simple, smooth, and fit closely together. The internal sting is differently formed according to the peculiarity of its function. In the Tenihredonodea it diverges most in form. In these it should not properly be called a sting, but a saw, and indeed earlier entomologists have compared it with this tool. It consists (PL XXIV. f. 8.), like the sheath, of two valves (a, a, and b, b), between which at their base there lies a short triangular process (c). Each internal valve has the same form as the sheath enclosing it, but it is smaller, so that it can be entirely embraced by it. The inferior edge of the inner valve is finely toothed (PL XXIV. f. 9. ), very sharp and narrow, inwardly sepa- rated by a projecting line from the remaining very smooth surface of the valve. The exterior has likewise a corresponding projecting ridge (the same, I), b}, which, like the ridge, is finely ajid sharply toothed ; 198 ANATOMY. raised lines run over the whole of this surface from tootli to tooth, and from the elevated ridge to the superior edge, which makes the whole exterior surface even, arid gives it the appearance of a fine file. With this saw-like apparatus the Tenthredo cuts the substance of leaves, letting an egg drop in, which is there developed that it may subsequently feed upon it. The short triangular process forms merely a key-stone to the margins, gaping at the base, and is of no importance to the function of the organ ; but it is necessary to men- tion it, as it is of great consequence in the structure of the sting in the rest of the Hymenoptera. If we examine the projecting sting of the Ichneumons, for example, Pimpla (PI. XXIII. f. 12 14.), we first observe the two exterior valves, (f. 14. a, a,) and between them, a fine horny sting which is a little dilated at its extremity (f. 12.). This sting was long considered simple, and even Gravenhorst, in his monograph of the European Ich- neumons, describes it so *. But it also is double ; the upper part (f. 13. a. and 12. .) is channelled beneath, completely smooth, and only at its broader point beset with small teeth ; the lower (the same, ,) much finer portion is a hair-shaped very pointed bristle, which lies within the channel of the superior one; this also is broader in front and lancet-shaped, and fits into a cavity of the upper part of its own shape. There is thus truly a passage in the aculeus, but so narrow an one that no egg can pass down it, and in this cavity how should it move along ? The egg merely slides down the superior channel, and is secured and pushed on by the inferior bristle pressing against the channel from the base towards the apex, pushing the egg above it. But, to refer this structure back to that described in the saw-flies, we must conceive the two internal valves as united in the superior simple half tube, and the bristle as the elongation of the central process at the base of the valves. Its structure is still more artificial in Sirex and the Bees. In Sirex (PI. XXIII. fig. 5 11), in which the sting projects, we find likewise the exterior valves (a, fl) and the central aculeus (b). This again consists of the superior channel (c, c,) and the bristle lying within it, which is here double, (d.d.) All three are dilated at their end (f. "]}, the channel is split, and that portion as well as the bristle upon its entire " Ichneumonologia Europsea, torn. i. p. 89. " Hsec seta terebra est, et canali ccntndi longitudinal! instructa esse dicitur, per quern ova poueruntur." FKMALE ORGANS OF GENKRATION. 199 margin beset with short serrated teeth (f. 9 and 10). That the bee's sting is similarly formed, although it lies in the abdomen, is shown in Swammerdamm's figure *. Latreille cites the true aculeus in Sirex as doublet, but personal investigation will readily con/ince of his error and the correctness of our representation. The spirally twisted aculeus of Cynips (PI. XXIII. f. 15 18), according to the opinion of early entomologists, viz. of Roesel, differs in structure from that of the bee's only in that its apex, which is covered by valves beset with hair, projects above the abdomen. Its supposed spiral twisting consists in its base being somewhat bent ; the point however somewhat sinks, so that it represents the figure of an S. (f. 16. a section ; a, , the valves ; b, b, the two exterior setae lying in it ; c, the central one). The description of the aculeus of the Cicada still remains. Its form in C. Fraxini is as follows : the large triangular dorsal plate of the last abdominal segment (PI. XXIV. f. J.A.), which at its apex is bent down, covers from above the two double-jointed sheaths (the same, B. and c.). Both joints are connected together by a soft membrane ; the basal joint (f. 2. B. B ) is broader, shorter, and hollowed out ; the last joint (the same, c. c.) is longer, narrower, towards its apex somewhat broader, triangular, within hollowed in a channel. This last joint is free, but the first is connected by a joint to the ventral plate. Between these lie the aculeus (the same, D.), a horny, round organ, a little dilated at its base, and near its apex compressed, where at the edge it is toothed ; and this again consists of three horny ridges connected by soft membrane. A still larger one (f. 3, , a, seen from beneath, f. 5 from above), broader in front, and there likewise toothed at the margin, lies above and forms the channel ; two finer narrower ones, pointed at the apex (f. 3, b., b, from beneath, and f. 4 from above) lie in the pre- ceding, and project beyond it at the end, forming its apex (the same, f. 2 D.). They all form combined a tube capable of distension, in which doubtlessly the eggs are pushed down by the valves themselves after the aculeus has pierced the vegetable substance, for which purpose evidently it is armed at its apex with the strong teeth. This, therefore, is the structure of the ovipositor in the different groups of insects : in its investigation we have concluded our exami- nation of the female sexual organs, and pass now on to the male organs. * Bihlia Nsiturae, PI. XVIII. f. 3. f Gen. Cms. et Ins., vol. iii. p. 242. 200 ANATOMY. II. OF THE MALE ORGANS OP GENERATION. 146. WE have already indicated that the male sexual organs consist essentially of the same parts as those of the female. They also are divided into interior and exterior ; the former of which comprise the TESTES, VASA DEFERENT/A, VESICA SEMINALIS, and DUCTUS EJA- CULATORIUS SEMINIS ; and the latter, the PENIS and the PREHENSILE ORGAN connected with it, and placed at the sexual orifice. We will therefore now proceed to the consideration of the internal male organs of generation. A. INTERNAL ORGANS OF GENERATION. 147- THE TESTES. The TESTES are glandular white bodies generally present in pairs, and which secrete the spermatic fluid. They regulate themselves in form and structure according to the differences presented by the glandular organs in insects in general, so that the majority are long convoluted vessels; some take the form of fasciculi of blind filaments, and a few lastly appear as round glandular bags. Their structure is regulated by their exterior appearance. Vascular testes have, like all the glands of insects, two tunics ; the internal loose mucous one displaying a parenchymatous appearance, the exterior one smooth, but coarser in structure, and corresponding with the exterior muscular membrane of all internal organs. Round testes have likewise a smooth coating, which enclose a multitude of small vesicular bags in the cavities of which the sperm is secreted. As the testes are analogous to the female ovaries, we should conceive that they as well as the latter should stand in connection with the dorsal vessel ; but this has not yet been detected, although many forms of testes extend in delicate filaments upwards which may apparently be the indication of such a communicating thread, as is the case in the ovaries. The analogous importance of both organs, which is most strongly proved by the progressive metamorphoses of insects, to which we shall subsequently return, is evinced also by the situation of the testes in the MALE ORGANS OF GENERATION. 201 abdomen, as they occupy precisely the same place possessed by the ovaries of the female, namely, the lateral spaces in the abdominal cavity contiguous to the intestinal canal, yet inclining more towards the venter. Those only which are united into one testis lie directly in the middle of the body immediately beneath the nutrimental canal. With respect to their precise shape, having thus indicated their most general differences, and distinguished them as tubular or vesicular, they may be arranged under several chief forms with various subordinate differences, which the following classification endeavours to display. I. SIMPLE TESTES. The long testes which, in the early stages, are divided, approach more closely together in the progress of development, and, lastly, in the pupa state, unite into one single globular testis, (Pi. XXIX. f. 1.) the earlier separation of which is indicated by a ring upon its surface. Each of the hemispheres divided by this ring has its own peculiar duct, which unite afterwards together. This structure of the testes is peculiar to all the diurnal, crepuscular, and nocturnal Lepidoptera, as well as the Pterophori ; other moths (the Tinea) have them always separated. This testis consists, upon closer inspection, of a thick cellular mass, which is pierced everywhere by delicate ramifications of the tracheae. II. SEPARATED TESTES. The testes remain during the whole course of the insect's life separated from each other, and lie on each side of the intestinal canal. A. SIMPLE VASCULAR TESTES. Each testis is a simple filiform or wider vessel, which lies either extended at full length, or makes convo- lutions, but it sometimes is entangled in a hank. 1. Testiculi lineares (PI. XXIX. f. 2.). They lie stretched out, and are wider than the ductus ejaculatorius into which they pass by means of a sudden constriction, and run upwards in a conical point. (Libellula.} 2. Testiculi clavati. (PI. XXIX. f. 3.). Each testis is an obtuse club, which gradually contracts itself into the ductus ejaculatorius, and thus imperceptibly passes into it. (Cercopis, Tinea.) 3. Testiculi JUiformea. (PI. XXIX. f. 4.). The testis is a twisted filament, which lies wound up in the abdomen, and, before it passes into the duct, distends into a longitudinal sperm bladder, (b. Tipula.) 4. Testiculi spir ales. (PI. XXIX. f. 5.). They distinguish them- selves from the preceding merely by each filiform testis being twisted 202 ANATOMY. spirally, and originating in a superior free and very fine filament. (Ranatra.) 5. Testiculi furcatl (PI. XXIX. f. 6.). The testis here is also a twisted canal, which furcates at its extremity and extends into two short capitate ends *. (Apis mellifica.) 6. Testiculi convoluti. (PI. XXIX. f. 7-)- The filiform testis is very long, much longer than the abdomen, and convoluted into some- times a round (TJyticus), sometimes ovate (Calosoma) ball. (Carabodea Hydrocantharides.} B. COMPOUND VASCULAR TESTES. Each testis is a bundle of shorter or longer filiform or filamentary blind vessels, or bags, which all unite into one common duct. 1. Testiculi scopacci. (PI XXIX. f. 8.). The short blind processes which the testes form, are of equal length, and sit close together upon the upper side of a common duct. (Hydrophilm.) 2. Testiculi fasciculati. (PI. XXIX. f. 9.). The somewhat longer blind processes are tolerably equal in size, and are seated contiguously at one spot, namely, at the end of the funnel-shaped distended sperm duct. (Buprestis Trichodes, Clerus, Epidydimis in Locusta, PI. XXVIII. f. 5, .). 3. Testiculi stellati. (PI. XXIX. f. 14.). From the end of the simple sperm duct, short fine, star-shaped or radiating filaments originate, (Apate.) 4. Testiculi flosculosi. (PI. XXIX. f. 15.). The filaments at the end of the sperm duct are here short, distended bags, which are placed around the distension of the sperm duct, like the petals of a flower of the class Syngenesia. (Asida, Te.nebrio, (Edemera.'} 5. Testiculi imbricati. (PL XXIX. f. 10.). Short purse-shaped, smooth pockets, which pass over each other like tiles, clothe a broad compressed bag, which runs out into a short, at first serpentine sperm duct. (Locusta viridissima.) C. COMPOUND VESICULAR TESTES. Each testis consists of oval or round and large or small vesicles, which unite either by degrees together, or at one end of the there distended sperm duct. 1. Testiculi racemosi. (PI. XXIX. f. 11.). The bladders are * Suckow, in Heus. Zeitschr. f. d. Org. Physik. vol. ii. p. 234. PI. XII. f. 30. Arcording to Swammerdamm, Biblia Natur.v, the testes are kidney-shaped bodies. MALE ORGANS OP GENERATION. 203 tolerably large, pear-shaped, and open by degrees, sometimes several together, into the common sperm duct. The lower bladders are larger and longer stalked. (Staphylinus.} 2. Testiculi granulati. (PI. XXIX. f. 12 and 16.). The end of the sperm duct is dilated into a bladder, which is entirely covered with round, button-shaped blisters. (Blaps, Pimelia, Musca.) 3. Testiculi vesiculosi. (PI. XXIX. f. 13.). The long testis con- sists of several rows of little bladders, which are placed around the extremity of the sperm duct. In Semblis there are three rows of such bladders present. 4. Testiculi vesiculoso-cirrati. (PL XXIX. f. 7- 6.). The reflected end of the sperm duct feears several petiolated, larger, capitate bladders, and between these there are fasciculi of smaller, ramose vessels, the extreme ends of which originate from four delicate glandular bodies. (Silpha obscura, according to Leon Dufour.) D. CAPITATE TESTES. The testis consists of several sometimes round or long kidney- shaped glands, which lie at the end of the common sperm duct, or each duct bears but one such glandular body. 1. Testiculi capitato-simplices. (PI. XXIX. f. 17-)- Each testis consists of a single, differently formed glandular body. In Lytta and Meloii, this body is globose or uneven and granulated (f. 17-) ; in Sialis, Phryganea, and Apis (according to Swammerdamm), it is kidney -shaped, and the duct opens at the spot where the kidney is emarginate. 2. Testiculi capitato-gemini. (PI. XXIX. f. 18.). The sperm duct is furcate, and each branch bears a similar round glandular testis. Donacia and Callichroma have equal branches: in Lamia oedilis, the superior one is longer (f. 18). 3. Testiculi digitati. (PL XXX. f. 1.). At the end of the sperm duct there are five conical glandular bodies, which extend in long serpentine fine vessels. (Nepa.) This form is as it were intermediate between the capitate and vascular testes. 4. Testiculi capitato-compositL (PI. XXIX. f. 19 and 20.). The sperm duct gradually divides into several branches, each of which sends off one (Cetonia Prionus) or several capitate testes. (Lepisma Cicada,) 5. Testiculi capitalo-verticillati. (PL XXX. f. 2.). Each testis consists of several globose frequently-compressed glandular bodies, 204 ANATOMY. concave in the centre, each of which has its peculiar duct. All the ducts are of equal length, and unite at one and the same spot to a common sperm duct. The number of glandular bodies varies : we find six in Melolontha vulgaris and Oryctes nasicornis, nine in Trichius fasciatus, and twelve in Tr. nobilis, on each side. This form appears to be the most complete of all, whence it is peculiar to the beetles only. H8- THE EPIDYDIMIS. The epidydimis is likewise a glandular organ frequently formed upon the type of the true testes, and opens with a peculiar either narrower or wider duct into the common duct of the sexual organs. We find this organ in a few beetles only: its function also is not dis- tinctly known ; the few hitherto observed forms are the following. We observe the epidydimis most distinctly in Hydrophilus piceus (PI. XXX. f. 3). They are here two long oval pointed bodies, turned back about their centre, which contain within an exterior fine tense skin a second glandular one, forming many rather long and regularly successive little bags. Upon a first inspection, this body appears, from its narrow, contiguous and parallel bags, as a convoluted vessel, and as such Suckow erroneously explains it *. From this organ there originates a long broad bag, with at first a narrow but suddenly distending orifice, which appears to be formed like the tracheae of a spiral filament, but, upon closer investigation, displays a structure similar to the epidydimis. It also consists of two membranes, of which the inner parenchymous mucous membrane likewise forms narrow, parallel bags, which I almost consider as the actual secreting cavities. In them we find a yellowish finely granulated liquid, the secretion of this epidydimis. Both these bags (PI. XXX. f. 10. aa.aa.) open at the end of the common duct in front of the sperm bladder. (The same, a *. a*.) They are somewhat longer, or certainly quite as long as the testes with the sperm duct, and extended they are of about the length of the abdomen, but they are usually rolled spirally. Similar appendages are found in Lytta and Meloe, but the epidydimis here is a serpentine, lace-shaped vessel, which, upon the ventral side, empties itself into the vesicular distended point of union of both the conical * In Heusing., vol. ii. p. 232. MALE ORGANS OF GENERATION. 205 sperm ducts *. In Trichodes, the epidydimis is also a simple, very much convoluted vessel, without distension or appendages f. In Locitsta and Gryllotalpa, the epidydimis forms a convolution of vessels. In Gryflolalpa, each of the four thick testicular bodies appears to consist of one convoluted vessel. The superior one or epidydimis is smaller, conical, and provided at the end with a long free filament; the lower true testis is larger and kidney-shaped. Both display upon their surface evident windings of vessels, which are surrounded by a darker mass. Their ducts unite beneath the large testis into a small sperm bladder, into which also the thick convoluted gluten vessel empties itself J. In Locusla, each epidydimis consists of two divisions : the upper one (a.) is a fasciculus of long, snow-white convoluted vessels, which all unite by degrees into a tolerably large duct ; the lower one (6.), on the contrary, is an oval bag, the superior surface of which sends off short round, tolerably narrow, filamentary processes. The sperm duct empties itself into the neck of the bag, but the duct of both bags, as well as the short one of the upper fasciculated epidydimis, form likewise two short tubes, which speedily unite with the broad, almost bag-shaped ductus ejaculatorius. At this point of union, we find on each side a small round little bladder, which is the vesica seminalis. These are the different forms of the hitherto observed epidydimes : other vascular appendages of the male sexual organs we shall shortly investigate, and discern in them gluten organs. 149. THE VASA DEFERENTIA AND VESICA SEMINALIS. The ducts which connect the testes with the common ductus ejaculatorius, are called vasa deferentia, or sperm ducts. They are fine tubes, originally of very small circumference, which either retain a uniform size, or distend in front of their orifice, and widen into an oval, long bladder. This distension is called the vesica seminalis or sperm bladder. We can speak only of the number and length of the sperm ducts. With respect to their number, we observe where several testicular bodies are found. There are also at first several sperm ducts, all of which, either * See Brandt and Ratzeburg Arzeneithiere, vol. ii. PI. XIX. f. 12 and 13. e. e. f Suckow, as above, PI. X. f. 57. Ibid. PI. XII. f. 20. 206 ANATOB1Y. by degrees or at one spot, unite into one common duct. The first case is found only in the compound capitate testes ( T. cap. compositi), but universally here. Thus the twelve ducts of the twelve glandular bodies of Celonia aurata unite by degrees to a common sperm duct ; indeed some of them previously unite together before they empty themselves into the common duct. In Prionus (PI. XXIX. f. 19.) the single ducts empty themselves alternately into the end of the common sperm duct ; the same in Cicada, Latr., in which each branch bears several glands. The second connection of the sperm duct is peculiar to the verticillate testes : here all the single sperm ducts unite at the end of the common duct, consequently at one spot. It is similar in the double testes (!T. cap. gemini), where consequently the sperm duct furcates at its extremity ; the same in Blaps, where two equal branches are found, each bearing a testis, and then a third, longer originating from the fork, which, however, bears no testis. The length of the sperm ducts is subject to no less variety. They are short in all those instances where they do not exceed the length of the abdomen, and, consequently, make no convolutions, as for example, in Lucanus, Hydrophilus, Locusta, Callichroma, Libellula, Nepa, and, in general, where there are large testes ; moderately long, that is, from twice to three times the length of the abdomen, they are found in those instances in which the different appendages we are about to describe are wanting, for example, in Semblis, Sialis, Phryganea, and Cercopis ; long or very long in those testes which are smaller and composed of several bodies, or in general of a convoluted canal, for example, in Dyticus, in which they are about five times as long as the body, and, like the testes, convolute themselves into a small knot (PI. XXIX. f. 7- b.) ; then in Necrophorus and Blaps eight or ten times as long ; in Cicada, Lat. fourteen times as long ; and in Cetonia aurata, nearly thirty times as long. A short but very broad and indeed gradually distending sperm duct is found in Meloe and Lytta (PI. XXIX. f. 17. b.), whilst in other cases it maintains a uniform compass. The sperm bladder has generally a more muscular structure than the sperm duct. The size is proportionate to that of the testes, and is wholly wanting to the less compact sexual organs, where the narrow sperm duct passes into the common ductus ejaculatorius without any distension. It is wanting, for example, in the Carabodea and Hydro- canlharides, in Lucanus, the Capricorn beetles, all Lepidoptera, Libellula, Ccrcopis, and several others ; as a slight distension at the MALE ORGANS OF GENERATION. 207 end of the sperm duct, it appears in the Lamellicornia, in Senil/tix, Tipula ; as a large ovate distension, at the end of the sperm duct in Hydrophilus (PL XXX. f. 10.) and Apis ; as a peculiar appendage to the sperm duct, in Phryganea (PL XXX. f. 6. &.>.). In Lylta, Meloc, and many others, we find but one sperm bladder, which has originated from the union of both the sperm ducts ; into this the lace-shaped epidydimis then empties itself. 150. PECULIAR APPENDAGES. We perceive appendages to the male organs similar to those glandular ones we noticed above in the female sexual organs. With respect to their peculiar purpose, we know certainly as little as of the true function of the vessels accessory to the female organs ; but it is just as probable that here as there they are gluten secreting organs, and, consequently, glandular. That such appendages are not absolutely necessary, is proved by the circumstance, that, as in the female, so also in the male sexual organs, they are frequently entirely wanting, and that sometimes they correspond in both sexes, as in Musca, Donacia, Semblis ; in other cases are found only in the female, as in Tipula, Ephemera, and Nepa ; and in others again are found in the male alone, as in Pterophorus and Cercopis. This deficiency of them in one sex, when present in the other, speaks against the opinion of Suckow*, according to whom they secrete urine; for this would necessarily be peculiar to both sexes, but which does not invalidate their being gluten secreting vessels of the sexual organs, which in general in male individuals are much more numerous, and are of a different form and situation to those found in the female. These appendages are also found where urinary organs show themselves, as in the Carabodea and Hydrocantharides. Comp. 114. If we more closely investigate the number and the form of these appendages, their first and most important character is their almost symmetrical situation and equal number. Tipula and Blatta only, as far as our knowledge extends, make an exception to this rule ; as in Tipula (PL XXX. f. 14.), according to Suckow, an uneven clavate process is found at the point of union of both sperm ducts, which, according to all analogy, can be explained only as a gluten organ, * Housing , vol. ii. p. 248. 208 ANATOMY. particularly as in many other insects the same part appears in a similar form. In Blatta, according to Gaede *, there is a large bladder at this precise spot. The symmetrical gluten organs are, in the first place, double, and, indeed, short clavate processes,, which, at the point of connection of the sperm duct, empty themselves into the ductus ejaculatorius. We thus find them in Sialis, Ephemera, Lepisma, Nepa, Apis (PI. XXX. f. 8.), and Piophila casei, Meig., in which, however, the clavate bag has a lateral pocket. In the Carabodea and Hydrocantharides, it appears longer, indeed as long as the abdomen, proportionately narrower, and already making some windings. In the former, at least in Calosoma sycophanta, each bag is flat, somewhat depressed from its apex, spirally convoluted, and into it, shortly before its termination, the sperm duct empties itself (PI. XXX. f. 13.) ; in Dyticus, on the contrary, it is round, irregular, twisted, and with its opponent, as well as with the sperm duct, it is bound together. Still longer, and, consequently, more twisted, but otherwise uniform, they appear in Gryllotalpa, where they are at least twice the length of the short testes ; in Stratiomys, it is once and a half as long as the testes and the sperm duct ; in Tinea, equally long, but narrow and filiform. In all these cases, they unite with the sperm duct at one spot, to form a common ductus ejaculatorius. Longer than the testes, but likewise thin, narrow, and filiform, we find them in the Lepidoptera : here, consequently, they make several turnings, and then empty themselves in the sperm duct itself, a short space before its union with the ductus ejaculatorius. (PI. XXX. f. 12.) The Lamellicornia possess the longest. They here appear as two long narrow, much convoluted filiform vessels (PI. XXX. f. 9. 6.), which, towards their base, distend into a long oval occasionally broad bladder (Melolontha), which, together with the sperm duct, passes into the common duct at one spot. The length of this vessel is sometimes con- siderable ; for example, in Oryctes nasicornis, about twenty times as long as the body, but in Cicada, Lat., where we observe similar vessels only five times as long. The ramose is the last form of the single-paired gluten organs. We have already observed such in the female appendages in Elater and Hippobosca; among those of the males, we find them in the Capricorn beetles. In Callichroma moschatum, I found a thick tangle * Beitrage zur Anatomie der Insekten, p. 20. MALK OKGANS OF GKNKHATION. 209 of very fine vessels, which, upon opening the insect, was covered by the dorsal portion of the posterior end of the intestinal canal. Upon closer inspection I found that all these vessels were merely the branches of a main stem that was furcated, which was the case also with each branch, and I thus found eight successive furcations. The terminal ends I could not distinctly perceive, but they are probably loose. In Lamia cedilis, at least, where only one furcated vessel is found on each side, the branches are free, but unequal, the exterior one being shorter, and the interior longer, the stem emptying itself into the sperm duct (PI. XXX. f. 11.) ; and it is the same in Callichroma moschatum. Where there are two pairs of appendages, they display the same forms. In Ascalaphus Italicus they are, according to Hegetschweiler, four unequal, pear-shaped bladders, which empty themselves into the sperm duct : the smaller ones have besides a superior vascular appendage. According to Posselt *, two pairs of vascular appendages are found in Geotrupes stercorarius ; to Hegetschweiler, in Clerux alvearius ; to Gade, in Tenebrio molitor ; and also in Blaps morlisaga, Meloe and Lytta, in which they are short, but of unequal length, and one pair empties itself upon the upper surface, and the other pair upon the under surface, into the sperm bladder f. In Hydrophilus, there are also two pairs of unequal appendages ; the inner ones are shorter but broader, the exterior ones longer, and they furcate into two equal branches : both empty themselves between the sperm ducts, the testes, and the epidydimis, into the end of the common ductus ejaculatorius. (PI. XXX. f. 10. b. b. and bb. bb.). In Notonecta glauca there are even four pairs of equal vascular appendages; and in Buprestis mariana, according to Gade J, there are two pairs of vesicular ones and two pairs of vascular ones together. One pair of the first is very small, the other longer, clavate, and bent : also one pair of the vessels is bag-shaped, and the other filiform and tolerably long. All unite at one spot in the ductus ejaculatorius, into which also the sperm ducts, but at some little distance further back- wards, empty themselves. * Bcitrage zur Anatomic der Insekten, Pt. 1. f. 1G. f Brandt and Ratzeburg Arzeneithiere, vol. ii. 4 Pt. PI. XIX. f. 13. t Nova Acta Phys. Med., vol. xi. p. 331. ANATOMY. 151. DUCTUS EJACULATORIUS. The DUCTUS EJACULATORIUS SEMiNis is that tube which extends from the point of union of both sperm ducts or sperm bladders to the commencement of the penis. It displays in its structure coarser muscular fibres, and is of a more compact nature than the sperm duct. It is analogous to the egg canal of the female organs, and appears sometimes, like this, vesicular (Hydropkilus), and sometimes contracted by degrees, consequently clavate (Lucanus, Lylta'), sometimes simple and of equal width. In length it varies much, sometimes short, scarcely visible, yet broad (Locusta, Gryllotalpa), sometimes longer, but yet, in proportion to the other internal sexual organs, still short (Calosoma, Melolontha, Trie/tins); moderately long when it attains about the same length as the sperm ducts (Hydrophihts, Lytta, Meloe, Papilio) ; long, lastly, when it is longer, indeed considerably so than the sperm ducts (Lucanus, Lamia). The most remarkable form of the ductus ejaculatorius I observed in Lamia cedilis. In this it is about eight times as long as each sperm duct, and geniculated. But to display this remarkable structure most justly, I must extend my description to that of the entire sexual apparatus. If a male Lamia cedilis be opened from its back, we first observe in the centre the convoluted intestine, and contiguous to it, on each side, about the centre of the lateral space, two white testes. Both unite into a narrow sperm canal, which runs towards the anus, and there unites itself with the opposite one of the other side, after each has received a furcated gluten gland. After a short course in a direct line, the ductus ejacula- torius bends forward, runs in a serpentine direction up the central line as far as the abdominal nervous cord, but beneath the intestinal canal, as far as the thorax, and here again bends a second time, turning upon itself like a knot, it then runs back again in a gentle curve to the anus, there to pass into the penis. From its first bend, this duct is no longer free, but it is enclosed in a wider membranous tube, into which also pass eight delicate tracheae, the fine ramifications of which spread upon the duct, and accompany it as far as the second bend, after they having one after the other previously dispersed themselves in fine branches. But from its second bend, the ductus ejaculatorius is accompanied by a strong horny ridge, which lies in the superior portion of the enclosing tube, retaining it tensely distended, and which terminates only where it passes MALE ORGANS OP GENERATION. 2 1 I into the penis. In the other Capricorn beetles (for example, Cullichroma moschatum,} the ductus ejaculatorius is indeed much shorter, but like- wise twice geniculated. That portion from the point of connection to the first knee is wider, more vesicular, and transversely ridged, taking the place of the sperm bladder, which is wanting, to the equally wide sperm ducts ; the other, double as long but much narrower portion, bends forwards as far as the commencement of the sperm bladder, re-bends back to the anus, and then passes into the penis, having reached the spot of its first geniculation. The penis, or rather its exterior case, is united to this first knee by means of a muscle. We are as yet unacquainted with other remarkable or peculiar forms. B. EXTERNAL ORGANS OF GENERATION. 152. THE PENIS. Having already perceived a great variety of form in the female external organs of generation, we might expect to find this still more extensively the case in the male organs, had their parts been as widely investigated and described. But that which does not invite close inspection by its exterior or the problematical nature of its form, but much rather withdraws itself from the eye of the inquirer, and is con- cealed upon a first superficial examination, does not so easily excite curiosity and stimulate the desire for instruction, because it is not sup- posed to exist. This is the reason why the structure of the penis has been made less frequently the subject of description than the female ovipositor, although possibly there is no other so variously formed an organ, nor one subjected to such characteristic and generic dif- ferences. The PENIS of beetles consists essentially of two parts, namely, of the exterior horny case analogous to the bone in the penis of the dog, and the internal delicate membranous penis itself, which admits of being consi- dered the free ductus ejaculatorius. The exterior sheath alone is visible upon a first examination, as it entirely covers the internal tube and allows it only at its apex, where it is divided a little, to project. This sheath is clothed, either entirely or partially, by a delicate membrane (the prae- putium), which may be considered as a continuation of the inner mem- brane forming the cloaca. This membrane has also sometimes horny ridges to support it. Thus much upon the penis in general ; more will P 2 212 ANATOMY". be derived from the following particular description of it in individual insects. In Carabus (C. glabratus, Fabr., PI. XXV. f. 14.), in which the withdrawn penis extends to the commencement of the thorax, the prae- putinm extends only to the end of the fourth segment (the last connate one counted as two) ; it is wide, bag-shaped, truncated at its extremity, and is supported by two fine bones, which have the same shape as the bag. At the base both bones lie closely together, but they with their shanks so separate that the two shanks of the upper one pass to the upper valve of the cloaca, and those of the lower one to its lower valve. The basal portion of the penis projects beyond the upper portion of the bag, driving this before it, so that it is covered by a continuation of it. Besides, the sides of the bones stand in close connection with the exte- rior integument by means of muscles, which hold the prepuce back when the penis is pushed forward. Three horny pieces are also found in the case of the bag, one heart-shaped one beneath, exactly between the shanks of the bone, and the two others at the apex of the upper portion which clothes the free part of the penis. There are likewise bony processes which support the case of the produced part of the bag, and stand in flexible connection with the horny sheath of the penis. The apex of the produced portion of the bag is divided where the upper end of the penis lies, and through this aperture the ductus ejaculatorius seminis passes into the latter. The penis itself is a gently bent, horny cylinder, above round, dis- tended towards its end, and flattened with obliquely truncated extre- mities ; upon its lower or ventral side it has a longitudinal aperture, which is surrounded by a callous margin, which indicates the outlet of the ductus ejacnlatorius. Dyticus (PI. XXV. f. 5 10.) displays already important differences. The two valves which form the cloaca are much larger, the upper one is soft and ovate, the lower one harder, larger, and longitudinally divided into two lobes. Both lobes are placed upon a transverse horny piece', one wing of which encompasses the exterior margin of each lobe, and is bound to it as well as to the ventral plate by strong muscles. The prepuce of the penis lies between these two valves, which, as in Carabus, is a membranous bag, but the horny bones of which are differently formed, and display stronger muscular connections. The prepuce itself is held distended by two horny pieces. A broad horny arch, shaped to the bag, surrounds its whole circumference, but lies MALE ORGANS OP GENERATION. 213 lower down, so that the withdrawn penis projects beyond it ; the upper margin of this horny arch is somewhat reflected, and forms two pro- cesses, to which muscles are attached that assist to push the penis forward (PI. XXV. f. 7- a, a}. The second flat longitudinal horny piece lies in the lower part of the bag between the shanks of the arch (PI. XXV. f. 6. 6). If the prepuce be opened we first meet with the horny sheath of the penis, a bilobate organ gently bent from right to left, between the valves of which lies a similarly bent and pointed horny spine. Both valves are closely connected by membranes and muscles, and are themselves enclosed in a membranous sheath (PI. XXV. f. 9. .), which is withdrawn by means of a fine horny bone flattened at its end ; it so lies between the prepuce and the penis that it retains the skin when the muscles push the penis forward. The valves of the penis are thickly beset, upon the bowed inner margin, with long setae, which are placed in a close row, as is also the inner spine. This spine has, similarly to the above-described female ovipositor, an excavated channel., in which lies a fine lancet-shaped bristle ; both are connected together by means of flexible skin and muscles, and between the bristle and the channel is the outlet of the ductus ejaculatorius. This spine therefore is the true penis, and the two valves are its case. The penis of Hydrophilus (PI. XXV. f. 11 14.) approaches very closely in many particulars to that of Dyticits. The prepuce here also is a truncated bag, from the upper surface of which the penis projects. In the lower part of the bag lies a broad, shovel-shaped, horny plate, from the margins of which on each side a bone originates, which form the lateral limits of the bag ; upon the upper side, at the end, lies a triangular perforated valve, which forms also the superior valve of the anal aperture, and sends off two free lateral processes to the bone of the lower portion (c, c). The cloaca penetrates beneath this valve, and is separated from the penis merely by a fold of the prepuce. The penis itself consists of the bivalved sheath and the unequal spines lying between them. Upon the inferior side the valve borders upon a heart- shaped horny plate (G), which appears to form the support of the entire organ ; its lateral margins turn upwards, and a coarse skin is attached to it, which closes the canal of the penis from above. The valves (E, E,) of the penis itself are pointed downwards, they are bent, concave, horny bones, which are internally filled by membrane and muscles, which unite to them the central spine of the penis. The most central spine (F. P ; ) is not bivalved. as in Dyficns, but a perfectly closed tube, at the 214 ANATOMY. under surface of which runs a narrow spatel-shaped horny bone, and there is a hair-shaped one at its superior surface ; the aperture (JT) is enclosed by two small horny arches. In Melolontlia the penis is only half covered by the prepuce ; its case is posteriorly, particularly upon the upper surface, entirely horny, and distended like a bladder ; two processes originate from it, which are nearly conical, somewhat sloping, and furnished anteriorly with a knob ; these are contiguous beneath, and above they are united by a strons membrane : between them lies the membranous canal of the o penis, which consists of several folds of the ductus ejaculatorius *. In Callichroma moschatum the prepuce is a thin cylindrical bag, which in front is obliquely truncated, and it terminates above with a triangular horny plate. At each of its lateral angles a bone originates, which inclining forwards proceeds beneath to unite itself there with the corresponding one of the other side, forming a perfectly horse-shoe- shaped arch. The case of the penis, which is similarly shaped, lies entirely enclosed within this prepuce; it is likewise more membranous, but terminates in front with two horny valves, the broader and lower one of which entirely embraces the narrower superior one upon the lateral margin, and sends forward two flat processes into the skin of the case. The membranous canal of the penis lies within this case, as a continua- tion of the ductus ejaculatorius (PI. XXVI. f. 1 and 2.). Among the Orthopiera we find in Blatta the penis perfectly unsym- metrical. The sexual organs are only visible upon the removal of the dorsal plate, for they lie concealed between the two last ventral plates, and are protected on each side by the short, jointed processes ; we then observe a triangular irregular valve (PI. XXVI. f. 17, 18. o), which covers the passage to the sexual aperture from above, and contiguously, two other, likewise unequal, bags (the same, b and c), which protect the sides, and lastly, beneath, a hook bent upwards obliquely over these parts (the same, d, d). Upon closer examination the superior valve displays itself as a triangular membranous lobe supported by several horny pieces, at the anterior apex of which there is placed a stiff horny hook, which is curved backwards (PI. XXVI. f. 5). The inferior valve, standing opposite to this superior one, is a flat horny plate (f. 0. ), with which laterally the right dorsal valve which bends upwards (f. ti. /;) is united by means of a flexible membrane. The yet remain- * See Straus, as nhove, PI. III. I. 5., PI. V. f. 13., and PL VI. t. ]. MALE ORGANS OF GENERATION. 215 ing portion of the visible sexual organs is the penis (f. 7), consisting of a superior sheath formed by two horny pieces, which are united by a membrane (f. 7- '