The shank of the larva has the same structure, so that the object to be extracted is enclosed in a scabbard as awkwardly shaped as itself. Each spur is enclosed in a similar spur; each tooth engages in the hollow of a similar tooth, and the sheath is so closely moulded upon the shank that a no more intimate contact could be obtained by replacing the envelope by a layer of varnish applied with a brush.
Nevertheless the tibia, long and narrow as it is, issues from its sheath without catching or sticking anywhere. If I had not repeatedly seen the operation I could not believe it possible; for the discarded sheath is absolutely intact from end to end. Neither the terminal spurs nor the double rows of spines do the slightest damage to the delicate mould. The long-toothed saw leaves the delicate sheath unbroken, although a puff of the breath is enough to tear it; the ferocious spurs slip out of it without leaving so much as a scratch.
I was far from expecting such a result. Having the spiny weapons of the legs in mind, I imagined that those limbs would moult in scales and patches, or that the sheathing would rub off like a dead scarf-skin. How completely the reality surpassed my anticipations!
From the spurs and spines of the sheath, which is as thin as the finest gold-beaters' skin, the spurs and spines of the leg, which make it a most formidable weapon, capable of cutting a piece of soft wood, emerge without the slightest display of violence, without a hitch of any kind; and the empty skin remains in place. Still clinging by its claws to the top of the wire cover, it is untorn, unwrinkled, uncreased. Even the magnifying-glass fails to show a trace of rough usage. Such as the skin was before the cricket left it, so it is now. The legging of dead skin remains in its smallest details the exact replica of the living limb.
If any one asked you to extract a saw from a scabbard exactly moulded upon the steel, and to conduct the operation without the slightest degree of tearing or scratching, you would laugh at the flagrant impossibility of the task. But life makes light of such absurdities; it has its methods of performing the impossible when such methods are required. The leg of the locust affords us such an instance.
Hard as it is when once free of its sheath, the serrated tibia would absolutely refuse to leave the latter, so closely does it fit, unless it were torn to pieces. Yet the difficulty must be evaded, for it is indispensable that the sheaths of the legs should remain intact, in order to afford a firm support until the insect is completely extricated.
The leg in process of liberation is not the leg with which the locust makes its leaps; it has not as yet the rigidity which it will soon acquire. It is soft, and eminently flexible. In those portions which the progress of the moult exposes to view I see the legs bend under the mere weight of the suspended insect when I tilt the supporting cover. They are as flexible as two strips of elastic indiarubber. Yet even now consolidation is progressing, for in a few minutes the proper rigidity will be acquired.
Further along the limbs, in the portions which the sheathing still conceals, the legs are certainly softer still, and in the state of exquisite plasticity—I had almost said fluidity—which allows them to pass through narrow passages almost as a liquid flows.
The teeth of the saws are already there, but have nothing of their imminent rigidity. With the point of a pen-knife I can partially uncover a leg and extract the spines from their serrated mould. They are germs of spines; flexible buds which bend under the slightest pressure and resume their position the moment the pressure is removed.
These needles point backwards as the leg is drawn out of the sheath; but they re-erect themselves and solidify as they emerge. I am witnessing not the mere removal of leggings from limbs already clad in finished armour, but a kind of creation which amazes one by its promptitude.