coat is fo hard, as to fecure them from the dangers they would otherwife have to dread. I imagine, that the hemifpherical figure of the cornea anfwers the purposes of the cryftalline and other humours; and I believe that, in place of the different coats of the eye, each hexagon receives a particular branch of the optic nerve. The eves of other animals are move. able, but those of infects, are for the most

part fixed.

There is great art, and many things remarkable in the ftructure of the mouth in infects. There is almost as much diverfity in the figure of this organ, as there are different fpecies. It is broad, pointed, or long like the fnout of a pig; and this last of various lengths and shapes.

Many infects have a fort of lips, not only on the upper and under fide of the mouth, but at the fides. A great number have palpi at the mouth, by which they examine their food, and with which they introduce it, and they likewise use them for cleaning it. These palpi have several articulations, fome have two, three, four, five, and even more. Some infects have only two palpi, others four. The extremity of them is often round and clubbed. It is channelled in fome beetles, and oblong in others.

We find 'alfo, in the mouth of infects, a fort of jaws or pincers, (mandibula,) which ferve inftead of teeth. Thefe they ufe in comminuting their food, or in breaking other fubftances. But, though these inftruments are exceedingly fine and delicate, they are at the fame time very hard and ftrong. They are fo fharp that fome can pierce the hardest wood, and make holes for themfelves to live in. Thofe who live only on foft fubftances, have no use for teeth fo hard or fo fharp; accordingly, they are obferved to be blunt in fome beetles that live on rotten

wood,

wood. Thefe pincers, in fome infects, are exceedingly smooth and fhining; they pretty much resemble the fpur of a cock, as may be seen in the larva of the Hemerobius. Some have fmall teeth on the fide of thofe parts which form the pincers, and oppofite to one another. They are not broad like tho e in man, but pointed and curved, nearly like the teeth of a faw. Their number is not equal. Beetles have two Scolopendra three, and the larvae of dragonflies fix. The maxilla of fome infeels have at their bafe two fingular knobs, with a longitudinal recefs, into which the maxillæ can be folded, like the blade of a clafp-knife. When the infect would feize any thing, and for that purpote joins the two pieces of thefe pincers, they do not touch, in fome infects, except at the points; in others, which have them longer, they fold over each other.

Thefe pincers are are of great ufe to them; ferving them not only inftead of teeth, in breaking and comminuting the food they take, but for grinding many other fubftances, according to their neceflities. It is with these they feize their prey, and hold it faft. They are likewife arms both offenfive and defenfive. Those which make holes in the ground, employ them in removing the things that obftruct their progrefs.

There are fome infects of prey, (for they well deferve the name,) which, befides thefe pincers, have, at the mouth a fort of claws, with which they hold their booty, as birds of prey hold theirs with their feet. Others likewife have jaws (maxilla) fituated under the pincers, which are moveable, like them, but in a lefs degree.

I must not in filence pafs over the trunk, or, as others call it, the tongue of infects. Some, as the grafshoppers, carry it between their pincers. There

are

are fome that can extend and draw it in at pleasure The Lepidoptera roll it up very adroitly, between two bearded bodies that conceal and protect it: others place it along their abdomen, where there is a little furrow formed for its reception. This trunk is not always of equal length: fome have it very fhort, and fome longer than the whole body. When it is viewed through a microscope, it is found to be very curiously fabricated, and, in a manner, adapted to the way of life of the particular infect: All its parts are fo difpofed, that nothing is fuperfluous, nothing deficient. In fome, it is inclofed in a fort of sheath, which terminates in a very acute point, ferving to pierce the fubftances that contain their food. When they have done this, they open the fheath, and infert the trunk into the wound, that they may extract the juice. It ferves, therefore, as a fyphon to fuck the fluids thev ufe as aliment. And befides this, it ferves to prick, and to wound like a lancet. Though this trunk is fo fmall that it can hardly be perceived, except it be with a glass, it is, nevertheless, so hard, that it can pierce, without difficulty, the hardest and thickelt hide,

After the head, there follows the neck, the thorax and laitly the abdomen. The thorax is more or less hard in proportion as the habits of the infect expose it to a greater or lefs degree of attrition. Thofe which creep into clefts as the Cimices, have this part of the body fomething flat, that they may the more eafily penetrate. It is more rounded in others, and fome, like the Silphas, have it furnished with elevated margins, occafioning a pretty confiderable corref ponding furrow. The thorax in fome terminates in a point behind, and that of others is blunt or rounded, as in grafshoppers. Many have it fet with hairs, and others with minute elevations which defend it from the effects of violent friction. It is furmount

ed

ed in fome with a protuberance, with two angles, with a horn, or with bodies of a pyramidical or thomboidal figure.

In the abdomen of infects there are many things which merit attention; and in the first place those incifures from which these animals derive their name. These are called rings or articulations; they are formed with great art, and very much differ in appearance. Some are very clofe, and look like wrinkles, others are broad and long; fome are square and fome are furnished with a margin or rim; and often there is an opening difcoverable between the folds. All infects, as may be easily imagined, have not the fame number of these rings. Some have five, some fix, and fome feven; all caterpillars have ten, and the aphides of the cabbage twelve. Some Scolopendræ have twenty, fome forty or fifty, and a certain larva of a Tenthredo feventy-two.

Thefe rings are of effential ufe to infects. It is by extending and contracting these that they move. By contracting them they defend the delicate parts of their internal frame from the heat of the Sun, from rain and from wind. If they need heat or refreshment, they can procure either the one or the other by the dilatation of their rings which then allow a free paffage to the rays of the Sun, or the fresh air. As they can dilate themselves at pleafare they can receive the precife quantity of either they have occafion for.

There is fuch diverfity of. figure in the bodies of infects and they are fo wonderfully formed that an exact defcription of them would be impoffible. The body of fome, as the fpider, is of a spherical shape, that of others as the cocinella, is hemifpherical. Some are round and flat, as the pediculi of the bat, others

are oval; fome have the figure of an egg compref fed, and fome refemble the quill of a feather. Some have the body flat and fquare. The body of the infect called Hippocampus has four long and flat fides; that called the Corculum aquaticum is of the figure of a heart. Some are crooked like a hook, and are furnished with a long tail, or small bag at the posterior extremity; of this laft the Sphex fabulofa is an example The diverfity of colour in this part is not lefs remarkable, but we fhall-enter more minutely into this fubject hereafter.

Thofe infects which have no feet have in different places of their body, fmall points which ferve inftead of them; and with these they attach themselves to folid bodies, and keep faft to them. In horfe dung there is to be found a maggot about an inch in length, whofe body has nearly the figure of a cherry-ftone. This animal has fix rings by means of which it can elongate and contract itfelf like the pipe uled in fome places for decoying quails; the furface of each of thefe rings is garnifhed with fmall acute points; in fuch a manner that when the maggot chufes to raife them up, they penetrate the bowels of the horfe, and keep the infect fo firm, that it is not carried along with the forces.

The bodies of thofe infects which live in water are naturally covered with a fort of oil which prevents the water from adhering to them, and retarding their motion. Others have along their body fmooth or crenulated margins, fometimes knobs that not only ferve to preferve them from being hurt by attrition upon entring or going out of their holes, but alfo are an ornament. These are not quite fo large as a grin of millet, yet there is obfervable an affemblage of the most beautiful colours, and they refemble thofe little glafs balls filled with different-co

loured