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PAGE 63, 1. 13.

It is merely the external form. Although the changes which the external parts of infects undergo, in their different transformations, are the most remarkable, they are not confined to thefe parts alone. Very confiderable changes likewife take place in their internal parts, fome of which are elongated, others contracted; fome lofe their functions, others acquire new ones, and others entirely disappear.

PAGE 64, 1. 7.

Into four different claffes. The explanation of the four forts of changes mentioned in this chapter, is taken from Swammerdam, who expreffes himfelf on the fubject, nearly in the fame way with our author. Thofe who are not perfectly verfed in the different transformations of infects, will perhaps be at a lofs to comprehend what is here related. I fhall endeavour, in a few words, to give as diftinct an idea of them as poflible.

For this purpose, it is neceffary, in the first place, to know, what is properly meant by the ftate of nymph and chryfalis, fo often mentioned. By thefe terms is meant, a ftate of imperfection, attended femetimes with inactivity, inaction, abftinence and weaknefs, through which the init paffes, after having attained a certain bulk, and in which its. body receives the preparatives neceffary for its paffing to a ftate of perfection. All the external parts of the infect are then found enveloped, either with their natural fkin, or with a fine membrane, or with a hard and cruftaceous coat. In the first cafe, the limbs of the infect remain free, it preferves its power of acting, it eats, and its form is little different from what it was before. In the fecond cafe, the limbs of the infect are folded over its breaft, but feparate; it can neither eat, nor act, it retains hardly any traces of its former figure, and has only a confufed refemblance to that which it is going to affume. In the third cafe, the cover brings all there parts of the animal into one mafs; it makes it equally incapable of eating and acting; it has no refemblance, either to what it formerly was, nor to what it is to be. These three forts of change, are evidently very different, and yet, we have but two words in our language to diftinguish them by. We fay of the infects in the two firft cafes, that they are changed into nymphs, and of thofe in

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the last cafe, that they have affumed the form of chryfalids. To thefe terms, it would be proper to add a third, in order to mark the difference between the first and fecond cafes. It might be done, I think, very conveniently, by allowing the last to retain the name of nymph, and calling those of the first kind femi-nymph, or demi-nymph; a name which, perhaps, would not be inapplicable to them, confidering the fmali degree of change they have undergone. Grafshoppers, which, instead of the long wings they acquire, have fill only on their backs, the fmall cafes, in which thefe wings are formed, are nymphs of this kind; they may properly be called femi-nymphs. Thofe who have had an opportunity of examining a bee-hive, cannot fail to have remarked bees, ftill imperfect in the fhut cells; these are nymphs of the fecond order. The filk-worm furnishes a well-known example of infects under the form of a chryfalis.

Infects, which undergo no other metamorphofis, than that which has converted them from the foft substance of an egg, to a well-formed and living body, are those which conftitute the first class of transformations spoken of in this chapter. They increase in fize; the greater part caft their fkin; fome of their parts acquire a greater fize than the reft, and fometimes take a different colour from what they had before. This is almoft the whole change which thefe undergo.

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The transformations of the infects of the other three claffes do not terminate here: after having caft off their ikins, for the most part feveral times, and after having acquired their defined bulk, all become either femi-nymphs, nymphs, or chryfalids. They pass a certain time under this form, and upon quitting it, affume that of a perfect infect, capable of generation. It is from the diverfity which takes place in thefe three forts of changes, that the principal characters, which diftinguifh the infects of the fecond, from thofe of the first and third class are taken.

The infects of the fecond clafs, are those that pass thro' the ftate which I have called the ftate of femi-nymph. They do not undergo a transformation which is entirely compleat, but in their laft change, they have generally still all the members they had before, without having acquired any others, except they have got wings: and as we have already remarked, the femi-nymph differs little in

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form, from the animal which produced it. What always diftinguishes it moft, is, that there is feen upon its back, at the bafe of the thorax, the cafes in which the wings are formed, which before that, appeared but little, and often not at all. In other refpects, it walks, runs, leaps and fwims, as before. The difference between the femi-nymph, and the winged infect which it produces, is not always fo obfcure. In fome fpecies, it is even fo great, that it is with difficulty we can difcover a trace of its first form; but this is not general, and the greater part, in their last state, differ in no other material part from the nymph, but in the wings.

The infects of the other two claffes, do not enjoy the fame advantage with the other. They lofe the ufe of all their members when they enter upon their transformation, and have no resemblance to what they were before. An animal of thefe two claffes, which before had no legs, or had five, fix, feven, eight, nine, ten, or cleven pairs of legs, has now no more nor less than three pairs, which, with the wings and antennæ, are folded under its breaft, and there remain immoveable.

What diftinguishes thefe two laft claffes from each other, is, that the infects of the third clafs quit their kin, when they change into nymphs, or into chryfalids, and that thofe of the fourth change into nymphs under their fkin, which hardens round them, and ferves them then for a cafe.

Thefe are the principal differences which Swammerdam and the author find in thefe four claffes. They confift, to exprefs it in two words, in this, that the infects of the first clafs, after iffuing from the egg, undergo no other transformation that thofe of the fecond fuffer an incompleat change, and become femi-nymphs, before arriving at their ultimate form: that thofe of the third and fourth claffes, before arriving at their perfect ftate, become, the firft nymphs or chryfalids, and the others nymphs, by a total change of form, but with this difference, that thofe of the third clafs quit their fkin at becoming nymphs or chrysalideg and that thofe of the fourth become nymphs without quitting their skin..

M. de Reaumur, to whom Natural History is indebted for fo many beautiful discoveries, found, in the transformation of infects of the fourth clafs, a new character, which no one, perhaps, had obferved before, and which, I think, diftinguifhes them more effentially from thofe of the other

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clades,

claffes, than the changing into nymphs, without quitting their skin. He difcovered, that they undergo one transformation more than other infects: that before becoming nymphs, they affume under their skin, an elliptical form, or that of an elongated fpheroid, in which no part of the animal is difcernible; that in this ftate, the head, the thorax, the wings and legs of the nymph are inclosed in the interior cavity of the abdomen, from which they iffue fucceffively, by the anterior part, nearly in the fame way as the extremity of the finger of a glove, which has been drawn in, is pufhed out again. Thus, the infects of this clafs, are not folely diftinguished from others, by their changing into nymphs under their fkin: but principally, in that before becoming nymphs, they undergo a double transformation. According to this idea, the differences of the four orders of transformations may be reduced to terms fimpler and more eafily comprehended, by faying, that infects of the first order, after iffuing from the egg, attain their perfect state, without being previously disposed to it, by a change of form; that thofe of the fecond clafs are prepared for it, by an incompleat change of form; and thofe of the fourth, by a double change of form.

*Lyonet here gives examples of these four claffes of transformations. The firft is exemplified by the common earth-worm. The fecond clafs, by a dragon-fly, (Libellula puella.) The third, by infects of the three different orders: 1. A pfeudo-caterpillar, which feeds on the willow, with two and twenty feet, (Tenthredo marginata.) 2. A waterbeetle of the largest fize, (Dytifcus piceus.) And 3. A caterpillar with fixteen feet, which lives on the trunks of willows, oaks, &c. (Phalana Coffus.) The fourth clafs is illuftrated by a white maggot, which proceeds from the eggs depofited by the large blue flies in fleth, when it is about to turn putrid. (Mufca vomitoria.)

The celebrated Bergman, before he betook himself to the illustration of mineralogy, had been fond of the study of infects, and he has left us a claffification of larvæ, a concife view of which, it is hoped, it will not be improper to give in this place.

The metamorphofis of larvæ, says Bergman, confists in the excoriation, or depofition of the external skin of the infect, joined with a change of form. This, in general, is twofold, to wit, from the larva to the pupa, and from that,

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to the perfect infect. An infect, fubject to metamorphofis is called a larva, as long as it continues under the form it affumed, when it first came from the egg, though many of them, during that time, caft their fkin. It is called pupa, under the new form which it acquires, when it has thrown off the appearance of a larva.

Pupæ are either chryfalids, nymphs, or femi-nymphs. A hard, motionless pupa, that does not eat and fhews obfcurely the members of the future infect, is called a chryfalis. The nymph is a tender pupa, lying at reft, not eating, and which fhews clearly the feparate members of the future infect. But the femi-nymph is a running pupa, that eats, and is hardly different from the larva, except in having the vaginæ of the wings, which the larva wants.

The chief differences of larvæ lye in the feet, and in the head. As to the feet, fome larvæ want them altogether, others have them, differing in number and figure. We are not accustomed to fee animals with heads that undergo changes in the form; but this wonderful faculty is fhewn by entomology. For many larve have a membranaceous head, that often changes its fhape.

Larvæ may be divided into eight claffes, one of these, (the Mida) have a membranaceous head, all the reft have it hard or horny. The first clafs is called Bracti. The larvæ that belong to this clafs, have membranaceous and horny feet, of the former, always more than ten, of the latter, fix. All these change into nymphs, and afterwards become Tenthredos. The fecond clafs comprehends the Campe. Their character is, to have never more than ten membranaceous feet, furnished with hooks, and fix horny feet. Thefe change into chryfalids, and then become Lepidoptera.

Simulta is the name of the third clafs. These larvæ have fix horny feet, no membranaceous ones: the mouth furnished with teeth. Thefe change into chryfalids, nymphs or femi-nymphs, and at laft, belong to the orders Coleoptera, Neuroptera, or Aptera.

The fourth clafs is called Ipedes. Their character is fix horny feet, and no membranaceous ones. Mouth without teeth, furnished with a fingle roftrum. The Ipedes turn into nymphs or femi-nymphs, and thefe into infects of the Hemiptera order.

The fifth clafs are the Serphi. They have fix horny feet, and no membranaceous ones. Mouth without teeth, furnifhed

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