網頁圖片
PDF
ePub 版

which could not but injure their skin; they are likewise weapons of offence, others striking their enemies with them very forcibly. Lastly, in those that live under water, there are some that encompass their hairs with a bubble of air which serves them to come up more easily to the surface. The water beetles have hairs on the belly between which there are little particles of air. When these are numerous they descend to the bottom with difficulty, and when they reach it, they are obliged to hold by some substance to keep themselves there: but when, they loose their hold, the air carries them up to the surface.

Nature has endowed some insects with horns difc ferent from the antennae, having no nrtieulations. Some have but one placed on the head, and rising straight or recurved like a hook. Some have two placed on the forehead bending to the sides cr rising in a straight line. These horns are either short, smooth, or a little incurved like hooks, or branched like those of the flying stag. Sometimes they are of equal length, sometimes one is longer than the other. There are likewise insects which have three of these horns rising perpendicularly. They are not always situated on the head, but sometimes on the shoulders near the head. Lastly, in some insects they are immaveable, but moveable in others. These last can, by their means hold their prey as with pincers, and the former can remove any obstacle from their way.

CHAP. II, C H A P. II.

Sb C T I O N it.
s Of Thf Internal Parts Of Insects.

Let us now come to the internal parts of insects, and let jus scrutinize the inmost recesses of their structure in order to penetrate into the mysteries of nature. The taste is full of difficulty. Many of those parts are so small as to escape our sight. To discover them we must use the highest magnisiers. Besides, the eye is weakened by the continued contemplation of one object, and we seel this sensibly when we force ourselves to the task. Notwithstanding these difsiculties, however, Naturalists have discovered many things on our present subject; these I*shall detail, and add what I have learnt from my own observations.

If we separate the external skin from an insect with instruments, or throw it into warm water, that the skin may come away of itself, we shall sind that it covers many parts worthy of attention. And sirst in the head we discern the brain, the substance of which is so soft that it is not easily examined even with a glass. When we pierce the eyes of iclects with a pin 'there issues out a fluid, in some clear like water, in others red like blood. Under the skin is the flesh. It may well receive the name since it consists of sibrous rous parts soft and sometimes reddish as in other animals. The fibres are oblong parts, thin and slender like the finest thread; their use is to connect the other parts with one another, and to put them in motion. They resemble wrinkles in the form of rings, and are distinctly observable in insects when the muscles are inactive; but when these are in morion they stretch the fibres, and make them invisible. The excessive delicacy of thejfibres in insects has prevented hitherto our discovering whether they are enveloped with a fine membrane, like those of quadrupeds. In some insects these fibres are so short that rheir length is hardly equal to the breadth of three hairs; and therefore, they are not always to be seen, evea ■with a glass. As they serve to extend, end to contract the muscles, their structure must resemble that of a wire wound round a cylinder, when that cylinder is withdrawn. They vaTy their motion, folding themselves in a semi-circle, sometimes to the right, sometimes to the left, nearly like a number of small worms. This motion, however, is very inconsiderable, and the fibres hardly change their situation. After these, the flesh of insects appears, as in other animals. There are likewise small veins, which, joined to the nervous and fleshy fibres, compose the muscles.

Insects are destitute of blood, properly so called; because, the composition of that fubltance demands more preparation and elaboration than can be performed in a body to small as theirs;. but, in place of blood, they have certain viscid humours that serve the purposes of it. These: humours contain their animai spirits, and from them insects draw their nourifhmen*-. However subtile they may be, they are, nevertheless, endowed with considerable tenaciry. In -'. consequence of this qualify, the head of a fly, after being cut off, will adhere again to its body, if" stuck on, without, however, restoring it to lise. This g!u> tinous quality of the humours enables insects to live for a time, after having been cut into two or more pieces; it prevents a rapid evaporation, it retains the humours which still continue to circulate for a time in the members, which would not happen without this quality. And, that this quality actually reside* in the humours of insects, we may be convinced, by exposing them* when drawn from the animal, to the air, when they will so dry, in a sew minutes, as to become brittle like glue.

Insects have an artery, which is observable, runing along their back, and in which pulsaiion may be feen. The air produces in this artery the fame effect that blood does in circulation.

Insects eat and drink like other animals, a stomach is therefore necessary to them. This is norhing but an extremely thin and hollow bag. The aliments of insects pass from the gullet into this stomach, where they are digested and changed into a nutritive juice. Among quadrupeds, those that ruminate need more than one stomach, formed of several folds. It is the fame with insects; some of them are found to ruminate, and consequently, have more than one stomach. It is of this sort of insects that God permitted the Jews to eat. See Levit. Ch< xi. 21. and 22.

Many persons, not having observed a heart in infects, have denied that they have any: but this is rash. These animals have many parts, so very minute, that they cannot be discovered; may this not be the case wit's the heart? Besides, there are many species, in which this organ may be distinctly seen". Lastly, the humours circulate in insects, and the arteries have a sort of pulsation; they must, therefore, «itb,er have a heart or something analogous to it.

Lungs

Lungs have likewise been denied to Insects. But^ as respiration is necessary to every creature, and as if is carried on by meins of lungs, which are found in« all the other animals, we cannot doubt but insects have them likewise. They are not of the same size, nor the same structure in all creatures; and those of insects are larger, in proportion, than those of other animals. This organ is formed in all, of little vesicles, connected with one another. The air enters by the trachea, and goes out at the fame place. Insects likewise have a trachea, which terminates in , their lungs^ but it is not of the fame structure with that in other animals. In these last, it is formed of many cartilaginous rings; in insects it is nothing but skin, which can be dilated or contracted with ease. The lungS of other animals have branches, which, from the vena cava, disperse themselves through the substance of the lungs, in many smaller branches. ( Insects have the fame, and by means of these, the air is distributed to all their members.

In most insects, the ihteslirtes are a little different from those in the other animals. The minuteness of their bodies will not admit of so great a number. Accordingly, in many we find nothing but a tube, extending from the mouth to the vent, as may be seen in such as are transparent.' It would appear, however, that, with respect to the great gut, it is not in all of the fame figure, for the excrements of some caterpillars are round, or cylindrical, and those of others have five furrows. This could not happen but from the structure of the rectum, which is the mould that gives the fæces their figure.

Round this long tube, are many slender fibres, which answer the purpose of veins and windpipe.

Bees have, towards the extremity of the abdomen T a

« 上一頁繼續 »