Among the wingless insects of Linnæus, is one which he has called by a name which signifies that it has _got a leg in its tail_; and this is actually the fact, in so far as that these insects have an organ in their tail, which answers all the purpose of a leg. Some of these little creatures, which are black, may be often found in spring strewed in infinite numbers upon the surface of the water in ditches or pools; and may be seen jumping about on the surface of the water as if bewitched. At their tail is a fork-like organ, which is generally bent under the body; but when they spring up they do so by quickly unbending this fork, the resistance it meets with being sufficient to carry it to a certain distance. Another insect is provided with eight pair of springs in its abdomen; by means of which it can leap to a great distance with most astonishing agility. Here we shall conclude the external anatomy of the insect, in the imago state.
Perfect insects breathe. That this is so, the following experiments[Z] will satisfactorily prove. A spider and a fly were put into a glass jar, the mouth of which was closed all but a hole by which a tube was admitted. The tube was then connected with a pipe by which a supply of common coal-gas was poured into the jar, and when it was considered to be full of gas, and that all the air had been displaced, the tube was closed, and the insects were left shut up in an atmosphere of gas. In a few seconds both became very uneasy, the fly more particularly so; and in a few seconds more the fly began to agitate itself, to buzz against the sides of the glass, and to tumble over in the most extraordinary manner; the spider ran hurriedly about, as if astonished, and not knowing what to make of his new position; but presently he became very quiet, and, turning on his back, looked as if dead. For a minute or two the fly, which was a large, active, flesh-fly, continued its noisy evolutions, dashing itself, as if intoxicated, on every side of its transparent prison. At length, as if exhausted, it lay on its back, its limbs paralyzed, but the wings still moving with extreme rapidity, and causing it to spin round in the most singular manner. Ultimately it, too, became perfectly without motion. After the lapse of about ten minutes, fresh air was gradually let into the jar, and it became most amusing to watch the return of both these insects, which had previously been as it were in the very jaws of death, back to life again; twitchings of their limbs, and slight convulsive movements, were the first indications of returning activity; and in a few minutes more both insects, now placed in a perfectly pure atmosphere, were as lively as before the experiment, and were allowed to make their escape into the open air. With other insects the same effects were produced by saturating a piece of blotting paper with ether, and dropping it into the jar, which was immediately covered over. In several other experiments the newly-discovered powerful fluid _chloroform_, by means of which the operations of surgery are performed without pain, was employed; and it was remarkable to notice how quickly the insects were overpowered with the vapour of this potent liquid. In no instance was death produced by the gases or vapours employed. Wishing to destroy without pain a beautiful specimen of a goat-moth, it was first stupified with the gas, then transfixed with a pin, and again plunged in an atmosphere of gas all night long; but alas! for the unhappy insect, the morning dawned, and it was yet alive.