49* 



HISTORY OF INSECTS. 



it is afterwards to undergo. The throwing 

 one skin, and assuming another, seems, in com- 

 parison, but a slight operation among these 

 animals : this is but the work of a day ; the 

 other is the great adventure of their lives. 

 Indeed, this faculty of changing the skin, is 

 not peculiar to caterpillars only, but is com- 

 mon to all the insect kind ; and even to some 

 animals that claim a higher rank in nature. 

 We have already seen the lobster and the crab 

 outgrowing their first shells, and then bursting 

 from their confinement, in order to assume a 

 covering more roomy and convenient. It is 

 probable that the louse, the flea, and the spi- 

 der, change their covering from the same ne- 

 cessity ; and growing too large for the crust 

 in which they have been for some time enclos- 

 ed, burst it for another. This period is pro- 

 bably that of their growth ; for as soon as 

 their new skin is hardened round them, the 

 animal's growth is necessarily circumscribed, 

 while it remains within it. With respect to 

 caterpillars, many of them change their skins 

 five or six times in a season ; and this cover- 

 ing, when cast off, often seems so complete, 

 that many might mistake the empty skin for 

 the real insect. Among the hairy caterpil- 

 lars, for instance, the cast skin is covered with 

 hair ; the feet, as well gristly as membrane- 

 ous, remain fixed to it ; even the parts which 

 nothing but a microscope can discover, are vi- 

 sible in it ; in short, all the parts of the head; 

 not only the skull, but the teeth. 



In proportion as the time approaches in 

 which the caterpillar is to cast its old skin, its 

 colours become more feeble, the skin seems to 

 wither and grow dry, and in some measure re- 

 sembles a leaf, when it is no longer supplied 

 with moisture from the stock. At that time, 

 the insect begins to find itself under a neces- 

 sity of changing ; and it is not effected with- 

 out violent labour, and perhaps pain. A day 

 or two before the critical hour approaches, the 



time before it would be naturally cast, these tufts maybe 

 seen in a moist state, very similar to small wetted ca- 

 mel's hair pencils lying close to the inner skin, those 

 on the fore part of the body laid towards the head, and 

 from the fourth ring backwards in a contrary direction. 

 Swammerdam, Reaumur, and other naturalists, repeat- 

 edly tried the experiment of cutting off the hair from ca- 

 terpillars about to moult, without in the least affecting the 

 hairs on the new skin ; but when a foot or any other 

 member is accidently mutilated, it is also wanting in the 

 moulted caterpillar. It is a still more singular circum- 

 stance, ascertained by Swammerdam, De Geer, Lyonnet, 

 and Bonnet, that caterpillars and grubs not only cast 

 their external skins, but also that which lines their 

 breathing-tubes and intestines. " Some days," says 

 Bonnet, "before the change, the caterpillar voids, along 

 with its excrements, the membrane which invests the in- 

 terior of its stomach and intestines. I have also re- 

 marked, that during the moult, packets of the trachea! 

 vessels may be seen attached to the cast skin, and thrown 

 oil along with it." Insect Transformations. 



insect ceases to eat, loses its usual activity, 

 and seems to rest immovable. It seeks some 

 place to remain in security ; and no longer ti- 

 morous, seems regardless even of the touch. 

 It is now and then seen to bend itself and ele- 

 vate its back ; again it stretches to its utmost 

 extent ; it sometimes lifts up the head, and 

 then lets it fall again ; it sometimes waves it 

 three or four times from side to side, and then 

 remains in quiet. At length, some of the 

 rings of its body, particularly the first and se- 

 cond, are seen to swell considerably, the old 

 skin distends and bursts, till by repeated 

 swellings and contractions in every ring, the 

 animal disengages itself, and creeps from its 

 inconvenient covering. 



How laborious soever this operation may 

 be, it is performed in the space of a minute ; 

 and the animal, having thrown off its old skin, 

 seems to enjoy new vigour, as well as acquired 

 colouring and beauty. Sometimes it happens 

 that it takes a new appearance, and colours 

 very different from the old. Those that are 

 hairy still preserve their covering ; although 

 their ancient skin seems not to have lost a 

 single hair : every hair appears to have been 

 drawn like a sword from the scabbard. How- 

 ever, the fact is, that a new crop of hair grows 

 between the old skin and the new, and pro- 

 bably helps to throw off' the external covering. 



The caterpillar having in this manner con- 

 tinued for several days feeding, and at inter- 

 vals casting its skin, begins at last to prepare 

 for its change into an aurelia. It is most pro. 

 bable that, from the beginning, all the parts 

 of the butterfly lay hid in this insect, in its 

 reptile state ; but it required time to bring 

 them to perfection ; and a large quantity of 

 food, to enable the animal to undergo all the 

 changes requisite for throwing off these skins, 

 which seemed to clog the butterfly form. 

 However, when the caterpillar has fed suffi- 

 ciently, and the parts of the future butterfly 

 have formed themselves beneath its skin, it is 

 then time for it to make its first great and 

 principal change into an aurelia, or a chrysa- 

 lis, as some have chosen to call it; during 

 which, as was observed, it seems to remain for 

 several days, or even months, without life or 

 motion. 



Preparatory to this important change, the 

 caterpillar most usually quits the plant, or the 

 tree on which it fed : or at least attaches itself 

 to the stalk or the stem, more gladly than the 

 leaves. It forsakes its food, and prepares, by 

 fasting, to undergo its transmutation. In this 

 period, all the food it has taken is thoroughly 

 digested ; and it often voids even the internal 

 membrane which lined its intestines. 



Some of this tribe, at this period also, are 

 seen entirely to change colour ; and the vi- 

 vacity of the tints, in all, seems faded. 



