ePub 版

are oval ; some have the figure of an egg compi led. and (one resemble the quill of a feather. So have the iiody flat and square. The body of the insect called Hippocampus has four long and flat sides j that called the Corculum aqoatieum is of the figure of a heart. Some are crooked like a hooky and are furnished with a long tail, or small bag at the posterior extremity ; of this last the Sphex sabulofais an, example, The diversity of colour in this part is not less remarkable, but we shall enter more minutely intothk subject hereafter.'

Those insects which have no feet have in different places of their body, small points which serve in. stead of them ; and with these they attach themsclve* ^o solid bodies, and keep fait - to them. In horse dung there is to be fpqnd; a maggot about an inch h> length, whose body has nearly the figure of a cherry-stone, ThjS animal has six rings by means of which it can elongate and contract itself like t))e pipe uled irr some places for decoying tjuailsj the surface of each,of these rings is garnished with small acute points; in such a manner that when the maggot chuses to raise them up, they penetrate the bowels of the horse, and keep the insect so firm,that it is, not carried along with the fæces.

The' bodies, of those insect* which live in water are naturally covered with a sort of oil which preVents the water from adhering to them, and retard, ing their motion. Others have along th,ejr body; smooth or crenulated margins, sometimes knobs that not only serve to preserve them from being hurt! by attrition upon entring or going out of theii* hoses, •but also are an .ornament. These, are npt quite, so large as agn in of millet, yet there is observable art assemblage of the most beautiful colours, and they resemble those little glass balk filled with different Cqr - louredloured waters. Lastly some like the camel have a protuberance on their back.


But we shall find as much diversity in the parts •that remain as in those we have already mentioned. The extremity of the abdomen is not alike in all. Some have it smooth, in others it is set with hairs, longer or shorter according to the uses they, are destined for. In this place are situated the papillæ front which they draw the threads they use in their different webs. Some like the caterpillar of the Philaena Lmcephala have this part covered with a short of shield. Others have at the fame place a stiff membrane which assists them as a rudder to turn when flying to this side or that j and is to infects what the tail is to birds. Some have long slender bristles, one, two, three, or four j, and others a fort of horns, straight, bent or crooked in various insects. When these horns are touched, some like the caterpillar of the Sphinx Euphorbias can draw them in as snails <lo theirs. Others have more slender horns, either simple,or, as in theBlattaorientalis,articulated. These horns are of various use, for to some insects as the Gryllus eampestris,, they give intelligence when ai:y thing approaches them from behind, to others they are the organs of attachment to> solid bodies, to others of progressive motion. The extremity of the abdomen is likewise the situation of the sting in those insects which possess it; some have one, other* two, which serve as weapons of offence or defence. Some, as the Earwig, instead of a sting have a sort of pincers or forceps at the tail, with which they defend themselves, and seize their prey. Lastly some like the caterpillar of the Phal^na Vinula, have two tentacula, like a tworpronged fork.

I now come to the parts of generation in inst cts, jyhich jcaimot be passed over in silence. These are U a generally placed at the extremity of the abdomen in the male,s, though there are some that have them placed foi> wards under the belly. These parts in proportion to the body of the insect are larger in some than in others. Those of the females are situated, as in the males, generally towards the extremity of the abdomen, sometimes under it. They are covered wiih a fine down, that the male organs, which are exceedingly delicate, may not be hurt by the contact.

Some insects have likewise, at the extremity of the abdomen, a sting. In some it lies within the bo7 dy from which they can dan it forth when they have occasion to use it, in'others it is'altogether external. If short, it is placed underthe belly, where it lies in a groove like that which receives the edge of the blade of a pocket kniff. If long it sticks out behind, and is encloseH in a sort of case sormed of two very slender laminae like a tube clelt longitudinally. This tube terminates in a very sharp point, which opens to allow the sting to pass when it is used. This sting is bearded with very sharp points like the beards of a hook. These not only prevent the sting from being withdrawn, but make the wound more painful. It is formed of two sharp spears, which, being once inserted into the skin, penetrate further by means of their ftiarp points. At the base of the sting near the belly is found a small bag full of a strong and penetrating fluid. This the insect extracts when it has occasion, and injects it into the wound made by the tube of its sting, when tumour and pain succeed in consequence of the fermentation of this fluid. The tube of the sting is smooth in some, in others when viewed through a magnifier, it appears hairy. At the base of the sting in the abdomeri of the insect are found the muscles by which it acts.

AU insects do not make the sam^ use of the sting.

.. i "*v in; In the female for instance, it is the conduit through which the eggs are conveyed and deposited. It is often more than half an inch in length, hollow,Nand cleft in two: It terminates in a pointed knob, with which the insect makes a hole in the earth, or in a leaf large enough to hold her eggs. These she deposites, through the hollow of her sting, that the rugged earth or other matters may. not harm them. As it is open by means of the cleft at top, as%well as at bottom, and as the eggs do not descend by the pressure of the air, Nature has formed in it many half rings opposite to one another, which facilitate its descent. Insects contract these successively, begining with that nearest the abdomen, and making the eggs descend from one ring to another, by a sort of peristaltic motion. The cleft of this canal is almost invisible while the insects are alive, but it opens a little more when they are dead. The stint* of the female is incapable of wounding; that of the males alone has this power.

The females of all insects are not provided with such a conduit: those which deposite their eggs on the surfaces of bodies, discharge them immediately by the genital organs. None but those which deposite their eggs in the flesh, in other insects, in leaves, or in the earth, have occasion for such a tube, that they may introduce them as deep as is necessary.

Although the sting of the males is extremely sine, it is, nevertheless, strong enough to pierce hard substances, and I have been stung by a bee through a goat-skin glove. They use it as a pike or lance to annoy their enemies, or to defend themselves.

This tube or sting does not always serve as a channel for the eggs. There are some aquatic insects, such as the Nepa Cinerea, that have this part common iDon to both sexes, and which they use as a spiracle to inhale the fresh air. They are seen often pushing the extremity of it to the surface of the water, and when they descend, there rise little bubbles of air, which escape from them.

We have had occasion to remark above, that infects which have feet, have not always the fame number of them, but that they vary according to the different species. Those limbs are generally situated under the abdomen: we find, however, a particular order of insects, aquatic as well as terrestrial, that before their transformation, have their feet on the back. But no sooner have they divested themselves of their skin, and their feet, and are in a capacity tQ fly, than these appear under the abdomen.

AH insects have not the legs of the fame length. Some have them very short, with but one articulation. Such are all caterpillars, whose six fore feet, are not, strictly speaking, any thing but hooked points, and the eight hind feet have but a single articulation, which give* them the appearance of being mutilated. Some insects are likewise found that have them longet, with three articulations, as some spiders, mentioned by Pliny; four, as the Scolopendra morsitans; five, as in the Tipula motitatrix ; six, as in the Aranea Diadema: and sometimes, even eight. The feet of the fame insect are not always of equal length. The hind legs of most are longer than the rest.—Bees have them so long that they can carry them to their head, and put into their mouths the wax these legs are loaded with. This rule, however, is not sq general but that there are exceptions to it, the fore legs in some being the longest.

These legs are generally composed os three parts, the first is a kind of thigh, (femur.) It arises immediately

« 上一頁繼續 »