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defect in his system is, that the fourth class separates from the third, animals of the fame kind, and which have a much greater resemblance to one another, than those of different kinds, that constitute his third class. For while the third class is composed of lepidopterous insects, of beetles and flies, animals exceedingly distinct from one another, the fourth consists only of flies which are not comprehended in the third. Thus, flies which are animals of one genus, are found separated., and distributed into different classes, while butterflies and beetles, animals of different kinds, are found united in the fame class. This is certainly a very great defect, and it is further augmented, by Swammerdam's introducing into his fourth class, several flies, which, according to his own principles, ought naturally to have been ranged in the third.
Besides, as the state of chrysalis and nymph is, with infects, generally a state of weakness, and always of imperfection, and as moreover, it is the state under which they are the least known, and often with most difficulty found, because then they are for the most part enveloped in a cone, or hid in the earth, or in places where it is not easy to find them. I am os opinion, that this state is not a proper one for furnishing such distinctive marks as can be of any utility.
'III. Linnæus, in his Systema Naturae, divides insects into seven general classes. In the first class, he places all those which have covered wings, as she different forts of beetles: in the second, those that have naked wings, such as butterflies, dragon-flies, ephemeræ, wasps, ichneumons, and other flies. In the third, those which he names half-winged, the character of which is, that they have not all wipgs, and have no covers to them: in this class he enumerates crickets, grasshoppers, ants, bugs, scorpions. His fourth class comprehends insects that have no wings but limbs, as the louse, the flea, the spider, the lobster, the oniscus, and the millepied. The fifth includes the creeping insects, whose body Is naked, and destitute of limbs, as the tenia, the earthworm, the leech, the slug. The sixth contains both land ,and sea shelled animals, and his seventh and last, such as he names zoophytes, furnished with limb.s, such as the echinus, sepia, sea stars, &c.
[*As the system here alluded to, was what L'nnæus published in the first edition of his Systema Naturæ, and which
■ * \ lie afterwards changed for the beautiful system, now almoft
in general use, the editor thinks it needless to translate M.
Lyonet's remarks on it. A general view of that improved
^yiiem, it may net be improper to give in this place.
Linnæus was the first who gave the proper definition of an infect, and that definition has been adopted by all succeeding authors. Infects, according to him, in their perfect state, are animals with many feet, (i. e. more than four) Ijreathing by means of lateral spiracles, covered with an osseous eru$, instead of. skin, and their heads furnished with rooveable antennae, the organs of some kind of fail's. He divides the whole clals cf insects into seven orders. The-first, containing all the insects that pass with us, under the general Baine of beetles, he calls Coleoptera; these have four wings, the upper divided by a straight longitudinal suture, hard, and serving as Cafes for the more tender, under-wings. The second, comprehending all insects of the bug kind, grasshoppers, &c. he calls Hemiptera; these have four wings, the two iipper not so hard as those of the former order, nor divided by a straight suture, but lying over each other. The third includes butterflies,' and moths; k is called Lepidoptera, from the small scales which cover the wings. The fourth contains the dragon-flies, ephemerx, &c. they have four membraneous and transparent wings, without any sting, and are called Neuroptera. The fifth includes bees, wasps, &c. which have likewise sour membraneous wings, and are fur-r y.ilhed with a sting; this order has the name of HymenopUra. The sixth contains all forts of flies and insects with two wings only, and is thence called l)ipteia; and the seventh, containing spiders, crabs, &c, is called Aptera, from their Laving no wing;.]
IV. I come now to the division of our author; and I observe, that if he had no other design in this chapter, than to reduce to certain heads, the principal diversities in the forms of infects, nothing could hinder us from admitting his system; but, if in place of this, his intention was to give us a general plan of the divisions of insects, to serve as a rule to those who should propose to treat of them methodically, and to give their history compleat, I cannot enter into his ideas.
ELs first division distinguishes insects into those with wings, and those without wings. But of what use is this division, when it is allowed, that infects in general> are produced duced from the egg without wings, and that it is not, tils after having passed the greater part of their lives in thift state, that they acquire she power of flying? If the author understood, as Linnæus does, ,by insects without wings, such' as never have any, and by those with wings, such as get them sooner or later, his division might be received j but this is not the case. He ranks' among the insects without wings, those which having lived for a certain time without wings, acquire them afterwards, such as caterpillars, and various larvæ, which change into flies and beetles; so that an' insect which is placed in one of his general divisions to-day,' may belong to the other to-morrow, which makes his system confused, and more likely to lead to error, than to order.
He afterwards subdivides unwinged insects Into those Which have legs, and those which have none. But this second division has another defect, which we have taken notice of in two of the preceeding systems, to wit, that of including in one class, animals of very different appearance,' while it distributes into different classes, animals of very similar formsv We shall find, for example, the snails which1 undergo no transformations, united with various forts of maggots, which are changed into flies, while those pseudoCaterpillars, which also change into flit-s, (i. e. tenfhredos) are separated, and placed in the other division.
The author next distributes unwinged insects with legs into different classes, according to the number of their legsj but this division labours under the fame defect, that of separating animals,.that resemble one another, and of conjoining diffifnilar ones. We shall find, for example, caterpillars with sixteen, fourteen, twelve, and ten feet, although they1 all change into lepidopteræ, separated into so many classes, according to the number of their feet, while the caterpillar with ten seel, will be found included in the fame class withsome spiders, and those spiders will be separated from those that have only eight feet, which last, will, in their turn, be conjoined with mites and other animals, which have no resemblance to them in form. After having thus made some subordinate divisions of unwinged insects, the author goes on to those that have wings. Here he succeeds better i but as insects, considered before the time when, they receive their wings, have already been arranged by our author, under different classes, winch have no relation to those he assigns; signs them, after having acquired wings, a naturalist who proposed to follow M. Lester's division, would find himself very much embarrassed, to conciliate the two sorts of divisions of the fame insects so opposite to one another. He would be obliged t.o abandon one of them, unless he rather chose to follow the injudicious manner of Johnston, and to treat separately of the same ahimalsj first as creeping, and then as winged insects. , .. . . „,.'•,, .
I hope these few remarks will be sufficient to shew that many inconveniences would arise from adopting any of the four systems' of, insects, I have now mentioned. At. the fame time we cannot but be surprised to see a science which has been treated of, even since the days of AristotlCj make so little progress, as never to have hitherto been properly systematiled.,, We would almost be tqmpted to .believe the thing impossible, is it were not more reasonable to think that the defect proceeds from few people having given themselves the trouble of reflecting on it,. And this ought, to induce all who study insects to turn their attention to the subject, as a good systematic division is what the science, stands most in need of. The information which may be drawn from those authors who have not succeeded will 'serve to guide those who shall undert ake it after them." In order to make the attempt more easy, I have ventured to point out the faults of those systems which have been already devised. The small experience I have in the matter prevents me from entring the lists myself; but if I wereallowed to speak my own sentiments of the subject I think that os all the general characters which distinguish insects^ none is so proper to furnisti a first division as that remarkable difference, to wit that some undergo transformations, and others always preserve the same figure they had at first. This diversity supposes in them a disposition of organs, an internal structure, a mechanism so different that I believe nothing can more essentially distinguish them. According to this idea, then, we may arrange all insects into two classes j the first comprehending'^ such as undergo no metamorphosis ; the second those which appear successively under different forms. ,'
The first division thus established would furnish a vast; field for as many subdivisions as the nature of the subject; might require. I do not design to detail these here, buf^ shall content myself with giving one example, following a. fingie branch, by which I (hall descend to a particular species among those that are bell known.
The second class may be divided into two principal genera. The one will comprehend infects which undergo a partial external change of form; that is a change which is not so compleat but that there remain marks more or less distinct of their former figure. The other will contain those whose external change of form is so total and compleat, that no traces of their former figure can be perceived. These last will be of three sorts; insects which change into beetles, those which are transformed into flies, and those which become butterflies or moths. The insects of thW last fort will consist of caterpillars properly so called and Spanners, (Geometræ) The Spanners will be either of a regular or of an irregular figure. The irregulars will be cither those with twelve feet or those which Jcpart from the, cylindrical shape by turgescences or protuberances, and thus .of the rest.
Although I propose this first idea of the general divisions as what appears to me the most natural and the most practicable, it is not to be supposed that I give it as exempt from, faults. I am persuaded that difficulties will appear in every system that can be formed. The author of nature, wishing as it were to shew that he is above the laws and rules he hath himself established, seems sometimes designedly to depart from them •, hence it happens that however general the rules are on which a system is founded, there will always be found exceptions which will render that system imperfect in proportion to their number. Sometimes these exceptions are of so singular a kind, that it is impossible to foresee them, and nothing but experience can demonstrate them. Not to speak of any but such as I consider as difficulties in my own plan, who would suppose that among insects of the fame species, and which is still more remarkable of the fame sex, there would be found some who never change their form, and consequently belong to the first division, while others undergo a transformation, which by making them acquire wings, transfers them to the second division? This would appear singular, and yet the aphides, instcts in many respects remarkable, afford many examples of it. Who would think that there were insects, the females of which suffer no transformation, while"the ma'e suffers a total change of form ? Of this however we find an example in the glow,. warm, the male of which is of the beetle kind, and the
& f femajp