ther to eat. So ftrict a faft is undoubtedly neceffary to prepare them for the change they are about to undergo and this feems the more probable as they discharge all the fæces their inteftines are filled with, before they attempt the change.

The metamorphofes of all infects do not resemble one another, but are generally divided into four different claffes. The firft comprehends thofe infects which after being formed in their egg, without the aid of food, and which after having taken, by the evaporation of the fuperabundant humidity, the neceflary confiftence, quit that state and iffue from the fhell under the form they are to retain during life, without undergoing any other transformation. To this clafs belong fpiders, lice, fleas, the onifci, the Iuli, &c. The transformation of the fecond clafs confifts in this, that the infect which was enclofed under a difguifed form in an egg, and without food, after having been fortified by the evaporation of the fuperabundant humours, leaves the fhell and appears under the form of an Infect without wings with all its other appropriate members; which in this ftate eats and grows till having entred a fecond time into what is called the Nymph ftate, it iffues from that ftate with wings and is capable of propagating its fpecies. I include in this divifion, ants, dragon flies, grafshoppers crickets, the mole-cricket, cimices, aquatic flies, &c. In the third transformation, the animal, after having iffued from the egg where it alfo lay in a difguifed shape, and without food, appears under that of an infect which eats and grows, while the members of the animal into which it is to change, are formed under its skin, which it at last quits, and becomes a nymph or chryfalis; and then after the evaporation of the fuperfluous humidity, is transformed into its last ftate, which is that of a perfect infect. This clafs includes bees of all forts, gnats, beetles, butterflies,

and

and moths. In the laft fort of transformation, the infect, after having arrived at the nymph ftate, like thofe before mentioned, does not diveft itself of its fkin in order to enter into that ftate, but affumes the form of a nymph under its fkin, where it continues fhut up, till quitting two fkins at once, it comes forth in its perfect ftate. This is the metamorphofis which flies, Ichneumons, &c, undergo.

Befides these changes, infects feveral times, caft their fkins; but this does not happen to them all at the fame time or in the fame way. Some, as fpiders, change their fkins only once a-year; others as grasshoppers, and the cabbage, caterpillars change it four times; and others even fix times. The greater part quit it entirely, but fome retain it attached to the extremity of the abdomen, and carry it over their head to defend them from bad weather, or other infects their enemies. This is the cafe, as Frifch obferves, with the Caffida nebulofa. The manner in which they diveft themfelves of it, varies alfo according to the diversity of fpecies. In fome it is rent near the top of the head, and the infect puts it off as one draws off a stocking. In others it is firft torn under the belly, and they throw it over their head as one does a fhirt. The fpoils of many infects preserve exactly the figure of the animal, which is particularly remarkable in thofe of fpiders. Some of these caft fkins, are lined internally with a white membrane much more delicate than the outer one. When thrown off, they are fometimes fo contracted as not to retain a third of their former length; at other times they appear fwollen, and difcover nothing but the hole through which the infect made its exit.

When the infect has thrown off its laft fkin it appears in the state of a nymph or chryfalis: thefe

are only covers under which the animal is formed, and which it preserves till it has taken its natural shape. These nymphs are soft at first, and contain fome liquid matter which in time evaporates, and they acquire more confiftence; but in general they are very thin and fragile.

Infects in this ftate may be divided into two claffes. There are fome of a conical fhape, almost of the fïgure of a date; others of an angulated form, with sharp corners at the rings and anterior part, and little elevations at these corners. There is a great diverfity in their figure. Without mentioning those that are of the form of a date, fome have the appearance of a child in fwaddling cloaths laid in a cradle; others have the face of a man. Others resemble the head of a dog, a cat, a bird, a mouse' with its tail, and even of the Infect itself which is to proceed from it.

The limbs of infects are not folded with lefs art in chryfalids and nymphs than they are in the egg. It is wonderful to fee the artifice with which they are difpofed, and the wifdom which has contrived to lodge in fo finall a space, fo many different members without hurting them, or producing the least confufion. In fome we may perceive externally all the limbs of the animal it encloses; others are fo transparent that the infect is easily discoverable upon looking through it but others must be opened before we can judge of the infect they contain.

Great variety is remarkable in the colour of chry falids. Brown, yellow, red, green, white, violet and black are the chief; but it must be obferved that thefe colours appear in various degrees, and that all the different fhades of them may be perceived in different forts of chryfalids, and in fome mingled with fo much art, that the eye is aftonished in view: ing them. The ancients imagined that the beauty of

the

the colours in a chryfalis was a proof of the beauty of the infect it contained; but nothing is more deceitful; we might as well fay that the beauty of a cradle was an indication of the beauty of the child that flept in it. Befides, experience teaches us that a plain infect very often iffues from a gilded chryfalis, while another with a lefs fpecious appearance often ` produces a very gaudy one.

No motion is perceived in fome of thofe infects while they continue in this ftage of transformation; but as this incapacity of moving themselves might expose them to be devoured by their enemies, they shelter themselves under a stone, a root, or a piece of wood. This is not all, they make that fide which is expofed, fo round and tenfe, that worms cannot lay hold of them. They are not however all motionlefs. Some fpontaneously agitate themselves, and others do not move except they are touched. These last, on such occafions move their abdomen and fhake their heads as if to defend themselves, and intimidate their enemy. There are likewise fome (as the Dytifcus latiffimus) which when turned upon their back, inftantly replace themfelves, in their first fituation. Others, (as the Coccinella feptempunctata,) turn themfelves round for fome time. Others though they are in general motionless, if they are taken into the hand, feem to be revived by the heat which puts their humours in circulation, and makes them perform various contorfions. neither the one nor the other take the least nourishment during the time they continue in the pupa state.

But

The precaution of choofing a convenient place in order to preserve themselves from injuries, does not always appear to them fufficient; they fortify the place they have chofen with a kind of entrenchment against attacks from without. The method

of fome is to fufpend themselves by the tail to threads which they draw from their own bodies, and thus they are fafe from the attacks of creeping infects, and they hold fo firmly by these threads that they are not eafily detached. Others weave around them a web with large meshes, nearly resembling a fifher's net this keeps at a diftance from the centre fuch infects as might injure them, and prevents their being hurt by the fall of any body. These two precautions are peculiar to thofe only which have skins fufficiently thick to refift the inclemencies of the weather. Thofe which have not the fame advantage cover themselves with a particular fort of web. Some fpin cones of filk, others difcharge from the pores of their body a fort of long wool which covers them during all the time they remain in the nymph state. Many fortify these cones with their hairs, which they diveft themselves of, (as the Phalana Caja ;) and thofe that have no hairs, and alfo want filk, gnaw pieces of wood, and employ the fmall bits in fortifying the infide and outfide of their manfion, as is the practice of the Phalana aceris. Some of these cones are fo hard and fo well cenftructed that they are with difficulty torn; they may be properly compared to parchment. To connect the threads toge ther, they moiften them with a fort of gum which if fues from their bodies, and which gives their work the neceffary degree of hardness. The cones are not all of the fame figure. The greater part are oval or fpheroidal, but there are fome that reprefent an egg cut longitudinally. They are attached by the flat fide to fomething folid which may contribute to their fafery. The precautions of fome are not confined folely to this external one: in order the better to fhelter themfelves against the inclemency of the weather, they cover it with a leaf, or many leaves gathered together others enter into the earth and hide themselves there, but for fear of its falling, they either plafter the

walls