Part 1

[Illustration: _Printed by H. Howard, RA._

_Engraved by W. T. Fry._

_William Kirby. M.A. F.R. L.S. &c_

_Published by Longman & C^o. London, July, 1825_.]

AN INTRODUCTION TO ENTOMOLOGY:

OR

ELEMENTS OF THE _NATURAL HISTORY OF INSECTS:_

WITH PLATES.

BY WILLIAM KIRBY, M.A. F.R. AND L.S. RECTOR OF BARHAM,

AND

WILLIAM SPENCE, ESQ. F.L.S.

VOL. III.

_LONDON:_ PRINTED FOR LONGMAN, REES, ORME, BROWN, AND GREEN, PATERNOSTER ROW.

1826.

PRINTED BY RICHARD TAYLOR, SHOE LANE, LONDON.

ADVERTISEMENT.

The publication of the concluding volumes of the "Introduction to Entomology" has been unavoidably delayed by the continued ill health of one of the Authors, which has devolved upon the other a considerable increase of labour, and demanded a greater expenditure of time than would otherwise have been required: for though Mr. SPENCE put every facility in Mr. KIRBY'S power, and had drawn up a rough copy of every Letter belonging to his department; yet, as most of them had been written several years ago, many curious facts, and a great variety of interesting information subsequently derived from various sources, were necessarily to be inserted, and the whole to be prepared for the press.

When the thousands of objects that were to be examined, and many of them repeatedly, in composing the Letters on the External Anatomy of Insects, are considered, it will not appear surprising if some errors should have crept in; especially as Mr. KIRBY was deprived of the effectual help formerly derived from the acumen, learning, and judgement of his esteemed coadjutor, by his lamented and protracted indisposition: but it is hoped that these errors will be found of minor importance, and not to affect any general principles advanced. The same remarks are also in part applicable to the Anatomical and Orismological Tables (VOL. III. p. 354-393, and VOL. IV. p. 257-354), which were drawn up by the Authors jointly many years ago, before any other portion of the work was composed, but which have, especially the former, required considerable alterations and additions in consequence of subsequent observations and information.

It will not be amiss here to state, in order to obviate any charge of inconsistency in the possible event of Mr. KIRBY'S adverting in any other work to this subject, that though on every material point the authors have agreed in opinion, their views of the _theory of instinct_ do not precisely accord. That given in the second and fourth volumes is from the pen of Mr. SPENCE.

It was originally intended, as mentioned in the Preface, to have given a complete list of Entomological works, of which a large portion was drawn up; but the great length to which more important matters have extended, has rendered necessary the intire omission of this list,--an omission in some degree compensated by the catalogue of _Authors quoted_, which comprises most of the standard Entomological works.

ERRATA.

Page. Line.

29 27, _for_ Pseudo-c_o_rdia _read_ Pseudo-c_a_rdia.

33 7, _for_ 1/12 _read_ 1-1/2.

35 7 and elsewhere, _for_ Gigas _read_ grandis.

46 16, _for_ number and situation _read_ in some respects.

98 6, _for_ Furtina _read_ Jurtina.

121 note^d, _for c read c´._

135 note^b, _for_ XXIV. _read_ XXIII.

137 note^a, _for_ 17 _read_ 18.

251 4, _for_ ten _read_ nine.

378 10, } _for_ frœnum _read_ frænum. 359 21, }

422 note^b, _for_ a´ _read_ a´´.

425 note^b, _for_ b´´ _read_ b´.

471 1, _dele_ Pelecotoma.

10, _for_ orbicular _read_ subtriangular.

512 antepenult. _After_ genera _insert_ except in some _Acridæ_, as _A. viridissima_.

562 note^c, _for_ πνεω _read_ πνυμι.

606 5, _for_ Heteropterous _read_ Homopterous.

DIRECTIONS TO THE BINDER.

The Synoptical Table of the Nomenclature of the Parts of the External Crust of Insects should be placed opposite to page 354.

Plates VI-XX. should be placed in this Volume, and the remainder in the Fourth.

It is however suggested to Purchasers, that in binding complete Sets of the Work, a separate Volume may be formed of the Synoptical Table, the Plates and their Explanations, and the Indexes.

CONTENTS OF VOL. III.

Letter. Page.

XXVIII. Definition of the Term _Insect_ 1-51

XXIX. States of Insects. _Egg state_ 52-104

XXX. The same Subject continued. _Larva state_ 105-237

XXXI. The same Subject continued. _Pupa state_ 238-290

XXXII. The same Subject continued. _Imago state_ 291-347

XXXIII. External Anatomy of Insects. _Terms and their Definition_ 348-393

XXXIV. The same Subject continued. _The Head and its Parts_ 394-528

XXXV. The same Subject continued. _The Trunk and its Parts and Organs_ 529-697

XXXVI. The same Subject continued. _The Abdomen and its Parts_ 698-720

NOTICE RESPECTING VOL. I. AND II.

It being judged expedient, since the publication of the last Edition of the first and second Volumes of this Work, to adopt a new plan with respect to the reference letters of the Plates, the Reader is requested to make the following corrections in those Volumes.

VOL. I.

Page. Note.

125 ^e, _for_ f, d _read_ a´´.

273 ^a, _for_ a _read_ _a_.

395 ^a, _for_ 29, 30 _read_ 13.

VOL. II.

244 ^c, _for_ a _read_ _a_.

319 ^b, _for_ 10 _read_ 14.

348 ^a, _for a read e´´´._

353 ^a, _for_ 7--. _read_ 16--.

366 ^b, _for a read s´´, v´´´._

^c, _for b read t´´._

405 ^a, _for_ 1.8. aa _read_ 18. _c_†.

^b, _for_ bb _read_ _q´´´_.

406 ^e, _for_ bb _read_ _C´´_.

407 ^e, _for_ cc _read_ _C´´ C´´_, which represent the bundles of muscles in connexion with the drums. In the above figure the mirror is the part directly under those bundles.

AN

INTRODUCTION

TO

ENTOMOLOGY.

LETTER XXVIII.

_DEFINITION OF THE TERM_ INSECT.

What is an insect? This may seem a strange question after such copious details as have been given in my former Letters of their history and economy, in which it appears to have been taken for granted that you can _answer_ this question. Yet in the scientific road which you are now about to enter, to be able to define these creatures technically is an important first step which calls for attention. You know already that a butterfly is an insect--that a fly, a beetle, a grasshopper, a bug, a bee, a louse, and flea, are insects--that a spider also and centipede go under that name; and this knowledge, which every child likewise possesses, was sufficient for comprehending the subjects upon which I have hitherto written. But now that we are about to take a nearer view of them--to investigate their anatomical and physiological characters more closely--these vague and popular ideas are insufficient. In common language, not only the tribes above mentioned, but most _small_ animals--as worms, slugs, leeches, and many similar creatures, are known by the name of _insects_. Such latitude, however, cannot be admitted in a scientific view of the subject, in which the class of insects is distinguished from these animals just as strictly as beasts from birds, and birds from reptiles and amphibia, and these again from fishes. Not, indeed, that the just limits of the class have always been clearly understood and marked out. Even when our correspondence first commenced, animals were regarded as belonging to it, which since their internal organization has been more fully explained, are properly separated from it. But it is now agreed on all hands, that an earthworm, a leech, or a slug, is not an insect; and a Naturalist seems almost as much inclined to smile at those who confound them, as Captain Cook at the islanders who confessed their entire ignorance of the nature of cows and horses, but gave him to understand that they knew his sheep and goats to be birds.

You will better comprehend the subsequent definition of the term _Insect_, after attending to a slight sketch of the chief classifications of the animal kingdom, more especially of the creatures in question, that have been proposed. That of Aristotle stands first. He divides animals into two grand sections, corresponding with the _Vertebrata_ and _Invertebrata_ of modern Zoologists: those, namely, that have blood, and those that have it not[1]:--by this it appears that he only regarded _red_ blood as real blood; and probably did not suspect that there was a true circulation in his _Mollusca_ and other white-blooded animals. His _Enaima_, or animals that have blood, he divides into _Quadrupeds_, _Birds_, _Fishes_, _Cetacea_, and _Apods_ or reptiles; though he includes the latter, where they have four legs, amongst the quadrupeds[2]; and his _Anaima_, or animals without blood, into _Malachia_, _Malacostraca_, _Ostracoderma_, and _Entoma_. The first of these, the _Malachia_, he defines as animals that are externally fleshy and internally solid, like the _Enaima_; and he gives the _Sepia_ as the type of this class, which answers to the _Cephalopoda_ of the moderns. The next, the _Malacostraca_, synonymous with the _Crustacea_ of Cuvier and Lamarck, are those, he says, which have their solid part without and the fleshy within, and whose shell will not break, but splits, upon collision[3]. The _Ostracoderma_, corresponding with the _Testacea_ of Linné, he also defines as having their fleshy substance within, and the solid without; but whose shell, as to its fracture, reverses the character of the _Malacostraca_. He defines his last class _Entoma_, in Latin _Insecta_, with which we are principally concerned, as animals whose body is distinguished by _incisures_, either on its upper or under side, or on both, and has no solid or fleshy substance separate, but something intermediate, their body being equally hard both within and without[4]. This definition would include the _Annelida_ and most other _Vermes_ of Linné, except the _Testacea_, which accordingly were considered as insects by those Zoologists that intervened between Aristotle and the latter author. The Stagyrite, however, in another place, has expressly excluded all _apods_[5]. From other passages in his works, it appears that he regarded the _Vermes_, &c. either as _larvæ_, or as produced spontaneously and not _ex ovo_[6].

This definition of an insect, though partly founded on misconception, as well as his primary division of animals in general, is by no means contemptible. If you look at a bee or a fly, you will observe at first sight that its body is _insected_, being divided as it were into three principal pieces--head, trunk, and abdomen[7]; and if you examine it more narrowly, you will find that the two last of these parts, especially the abdomen, are further subdivided. And this character of _insection_, or division into segments, more or less present in almost every insect[8], is not to be found (with the exception of the _Crustacea_, which Aristotle distinguishes by the nature of their integument and its contents) in any of the other classes into which he divided animals without blood. It was on account of this most obvious of their characters, that these little creatures were in Greek named _Entoma_, and in Latin _Insecta_; and from the former word, as you know, our favourite science takes the name of _Entomology_.

Pliny adhering to the definition of Aristotle, as far as it relates to the _insection_ of the animals we are speaking of, expressly includes _Apods_, as well as _Aptera_, amongst them[9]; and in this was followed, without any attempt at improvement, by all the entomological writers that intervened between him and the great Aristotle of the moderns, Linné.

This illustrious naturalist, aware of the incorrectness of the primary divisions of the animal kingdom founded upon the presence or absence of blood, establishes his system upon the structure of the heart, and upon the temperature and colour of the circulating fluid. He divided animals into two great _sections_ or _sub-kingdoms_, each comprising two _classes_. His _first_ section included those having a heart with _two_ ventricles, _two_ auricles, and _warm_ and red blood, viz. the _Mammalia_ or beasts, and the _Aves_ or birds. His _second_, those having a heart with _one_ ventricle, _one_ auricle, and _cold_ and red blood, namely, the classes _Amphibia_, which included reptiles, serpents, &c. and _Pisces_ or fish. His _third_, those having a heart with _one_ ventricle and _no_ auricle, and _cold white_ sanies in the place of blood, namely, his classes _Insecta_ et _Vermes_, including the _Invertebrate_ animals of Lamarck. Thus the first of Aristotle's great divisions he increased by the addition of a new and very distinct class, the _Amphibia_, by which some ground was gained in the science; but as much was lost by his compressing the four classes of which the last consisted into two, by which the natural classes of _Cephalopoda_ and _Crustacea_ merged under _Insecta_ and _Vermes_. Linné was not aware of the extraordinary fact, that the _Cephalopoda_ have three hearts; and that though the _Crustacea_ and _Arachnida_ have a circulation, _Insects_ have none, or he would never have taken this retrograde step.

Indeed Linné's definition of an _Insect_ is, in many most material points, inapplicable, not only to the _Crustacea_, but to many other animals included under that denomination. This will appear evident from a very slight examination. Thus it runs: "_Polypod animalcula, breathing by lateral spiracles, armed every where with an osseous skin, whose head is furnished with movable sensitive antennæ_[10]." Now of this definition only the first member can be applied to the whole class which it is meant to designate; for the entire genus _Cancer_ L., which, with some others, forms the class _Crustacea_ of the moderns, does not respire by _spiracles_ at all, but by _gills_; and the same in some degree may be said of spiders, scorpions, &c. With the last member of the definition Linné himself must have been aware that a large number of what he conceived to be insects were at variance, as mites, spiders, and many other of his apterous tribes: though from some very recent observations of M. Latreille[11], there seems some ground for thinking, that in these the antennæ are represented by the mandibles, palpi, &c.[12], and to the soft flexible, coriaceous or membranous skin of a vast number of insects, the term _cutis ossea_ is by no means applicable.

Evident as these incongruities are, when the Herculean task which Linné imposed upon himself, and the vastness and variety of his labours, are considered, they become very venial. Indeed, unless he had divided his class _Insecta_ into two or more, it was impossible to define it intelligibly to ordinary readers, otherwise than nearly in the terms which he actually employed; and these characters, restricted and amended by qualifying clauses, are still those to which recurrence must be had in a popular definition of the class, when separated as it ought to be from the _Crustacea_ and _Arachnida_.

Pennant, Brisson, and other zoologists, who, attending to _nature_ rather than _system_, saw the impropriety of uniting a crab or a lobster in the same class with a bee or a beetle, long since assigned the _Crustacea_ their ancient distinct rank. "But these changes," as Latreille observes[13], "being only founded upon _external_ characters, might be deemed arbitrary; and to fix our opinion, it was necessary to have recourse to a decisive authority--the _internal_ and comparative organization of these animals." It results from the observations of the most profound comparative anatomist of our age, M. Cuvier, that the _Crustacea_ and _Arachnida_ differ from insects properly so called, and particularly from those that are furnished with wings, in having a complete system of circulation, a different mode of respiration, and that they have a more perfect organization. Influenced by these motives, both Cuvier and Lamarck have considered them as forming two classes separate from insects. Treviranus, led by considerations founded on the organs of circulation, of respiration, and of generation, is of opinion that spiders and scorpions ought to form one class with the _Crustacea_: he observes, however, that the nervous system of all three is very dissimilar; and that in an arrangement founded on this circumstance, the organs of motion, and the external shape, even spiders and scorpions must be placed in different classes[14].

It is to be observed with regard to the _Arachnida_ of the French school, that the class as laid down by them includes several animals that have no circulation, and breathe by _tracheæ_, of which description are the mites (_Acarus_ L.), and the harvest-men (_Phalangium_ L.) &c.; and therefore it has been divided into two orders, _Pulmonaria_ and _Tracheana_; but if the definition from the internal organization be adhered to, the latter should either remain with the class _Insecta_, or form a new one by themselves. Yet the animals that compose the _Trachean_ order of _Arachnida_, their external form considered, are certainly much more nearly related to the spiders and scorpions than to any members of the class _Insecta_ at present known. This circumstance, perhaps, may seem to throw some doubt upon the modern system of classification.

I must further observe, that the assertion of Treviranus, which appears to intimate that the respiration of the _pulmonary Arachnida_ is the same with that of the _Crustacea_, is not quite correct, since in the latter the _branchiæ_ or gills are _external_, and in the former _internal_, the air entering by spiracles before it acts upon them[15].

It may not be amiss in this place to lay before you the principal points in which the _Crustacea_ and _Arachnida_ agree with _Insecta_, and also those in which they differ.

The _Crustacea_ agree with _Insecta_ in having a body divided into segments, furnished with jointed legs, compound eyes, and antennæ. Their nervous system also is not materially different, and they are both oviparous. They differ from them in having the greater insections of the body less strongly marked; in the greater number of legs on the trunk, the anterior ones performing the office of maxillæ: in their eyes usually on a moveable footstalk: their palpigerous mandibles; and their four antennæ at least in the great majority. But the principal difference consists in the internal organization and the fountains of vitality; for the _Crustacea_ have a double circulation, the fountain of which is a heart in the middle of their thorax[16]. They have too a kind of gizzard and liver, at least the _Decapods_[17], and their respiration is by gills. Genuine insects terminate their existence after they have laid their eggs[18]; but the _Crustacea_ live longer, and lay more than once.

The _Arachnida_ will be found to differ from insects more widely than even the _Crustacea_. They agree in their jointed legs and palpi; immoveable eyes; and in being covered with a coriaceous or corneous integument: but they differ in having a system of circulation; gills instead of tracheæ; their organs of generation double; and the females lay more than once in their lives. Their head also is not distinct from the trunk as in insects; they have no compound eyes; and their antennæ, if we admit the opinion on this head of MM. Latreille and Treviranus, that they have representatives of these organs, differ totally in structure, situation, and use, from those of the great body of insects. In the _Araneidæ_ or Spiders, their body seems to have no segments or incisure but that which separates the abdomen from the trunk; and in the _Scorpionidæ_ they are observable only in the abdomen. Other particulars might be enumerated in which these two classes differ from insects; but these will be sufficient to convince you that Aristotle and MM. Cuvier and Lamarck were justified in separating them.

The two last-mentioned authors made further improvements in Zoology. The latter, from the consideration of the general structure of animals, perceiving that Aristotle's _Enaima_ were distinguished from his _Anaima_, by being built as it were upon a vertebral column, very judiciously changed the denomination, which was indeed improper, of "_The Philosopher's_" two sub-kingdoms, into that of _Vertebrata_ or animals that have a vertebral column, and _Invertebrata_ or those that have no vertebral column. These he distributes into three primary divisions according to their supposed degrees of _intelligence_--Thus:

* _Apathetic Animals._ 1. INFUSORIA. 2. POLYPI. 3. RADIATA. 4. VERMES.

** _Sensitive Animals._ (_Epizoaria._) 5. INSECTA. 6. ARACHNIDA. 7. CRUSTACEA. 8. ANNELIDA. 9. CIRRHIPEDA. 10. MOLLUSCA.

*** _Intelligent Animals._ 11. PISCES. 12. REPTILIA. 13. AVES. 14. MAMMALIA.[19]

Profiting by the light afforded by the Aristotelian system, this eminent zoologist improved, we see, upon that of Linné, by resolving his _Insecta_ into three classes, and his _Vermes_ into seven, interposing the Linnean _Insecta_ between the four first and three last, in which he was not so happy, since as to _sense_ insects should certainly occupy the place he has here assigned to the _Mollusca_.

In the work from which I have taken this statement of Lamarck's system, that acute writer has given a sketch of another method of arrangement, in which he has made the first deviation from the beaten track of an unbroken and unbranching series. In the Supplement to the first volume, he has distributed the _Invertebrata_ in a double subramose series--one consisting of _articulate_, and the other of _inarticulate_ animals[20].

Upon Lamarck's system, most of the modern ones, with some variation, are founded. There is one, however, by a learned countryman of ours, that is more unique, _sui generis_, and I may add profound, than any that has yet appeared. I am speaking of that, you will perceive, of which our friend Mr. Wm. MacLeay has given a detailed statement in his _Horæ Entomologicæ_. In this he goes even far beyond what Lamarck has attempted in the above sketch, and substantiates his claim to be considered as one of those original thinkers, _rari nantes in gurgite vasto_, that do not appear every day. The following are the principal bases of his system.

1. That all natural groups, whether kingdoms or any subdivision of them, return into themselves; a distribution which he expresses by circles.

2. That each of these circles is formed precisely of _five_ groups, each of which is resolvable into five other smaller groups, and so on till you reach the extreme term of such division.

3. That proximate circles or larger groups are connected by the intervention of lesser groups, which he denominates _osculant_.

4. That there are relations of analogy between the corresponding points of contiguous circles.

This system he has represented by tables of circles inscribed with the five primary divisions of each group. His first table exhibits a general view of organized matter as distributed in the animal and vegetable kingdoms--Thus:

[Illustration]

Our learned author here divides the animal kingdom into what may be denominated five sub-kingdoms or provinces, in three of which (with the exception of the _Crustacea_ and _Arachnida_ belonging to his _Annulosa_) no circulation of blood is visible, but which obtains in the rest. These he names--

1. ACRITA, consisting of the _Infusory Animals_, the _Polypi_, the _Corallines_, the _Tæniæ_, and the least organized of the _Intestinal Worms_.

2. RADIATA, including the _Jelly-fish_, _Star-fish_, _Echini_, and some others.

3. ANNULOSA, consisting of _Insecta_, _Arachnida_, and _Crustacea_.

4. VERTEBRATA, consisting of _Beasts_, _Birds_, _Reptiles_, _Amphibia_, and _Fishes_.

5. MOLLUSCA, including the numerous tribes of _shell-fish_, _land-shells_, _slugs_, &c., which, from their mucous or gelatinous substance, from their nervous system and the imperfection of their senses, return again to the _Acrita_, though connected with the _Vertebrata_ by having a heart and circulation.

His next set of circles shows the sub-division of these five sub-kingdoms into classes--Thus:

[Illustration]

In this scheme the _osculant_ classes are those placed between the circles. In the _Mollusca_ circle two classes are still wanting to complete the quinary arrangement of that sub-kingdom. I am not sufficiently conversant with the details of the animal kingdom at large to hazard any decided opinion upon Mr. MacLeay's whole system, or to ascertain whether all these classes are sufficiently distinct[21]. My sentiments with regard to those of the _Annulosa_ I shall state to you hereafter.