The Insect World: Being a Popular Account of the Orders of Insects

The caterpillar of the Tiger Moth, or Woolly Bear, called by Reaumur Marte or Herisson Fig. {Chelonia caja^ Fig. 116), is covered with long inclined hairs. -T^arva ofof itsAcronyctacocoon. aceris taken out This caterpillar also makes use of its hairs for strengthening the tissue of its cocoon; but whether it feels the pain more acutely than the former, or whether it would

Fig. 116. — Larva of Chelonia caja.

suffer more, it does not tear out its hairs. It adopts another system; it cuts them. The caterpillar is then enveloped on all sides in its hair, which is to serve in the construction of its cocoon (Fig. 1 17).

Another species uses its hairs in the composition of its cocoon; but it adopts an entirely peculiar way of tearing them out, when the tissue of its cocoon has become a species of network of pretty closely packed rings. Reaumur one day saw one part of the cocoon bristling with hairs. These were the hairs of a part of the back of the caterpillar, which it had pushed through the rings of its cocoon. The caterpillar then moved about as if rubbing this part of its back successively in opposite directions against the interior surface of the cocoon. In this way the hairs were very soon torn out and kept retained in the rings of the cocoon. This cocoon is then bristly inside, and does not at all suit the future chrysalis, which does not like to be touched by any but smooth surfaces. The caterpillar then works

Fig. 117. with its head, to lay the hairs along

Larva of Chelonia caja forming its cocoon. the interior surface, and to keep them down by threads, which it draws over them. At another time Reaumur saw a small hairy caterpillar, which appeared to live on lichens, using its hair in another way. It tore them out to make its cocoon, but it was not to lay them down and work them into a tissue. It set them straight up

Small Caterpillar of the Pimpernel.

Fig. 119.— Cocoon of the same.

like the stakes of palisades, On the circumference of an oval space in which it was placed. Shut up within this palisade, it spun a ligh white web. This web supports the hairs, causing the greater part 0

LEPIDOPTERA.

them to curve at their upper extremity, in such a manner as to form a sort of cradle. It remains for us now to speak of the caterpillars that make their cocoons of silk, together with other materials. Reaumur saw the Pimpernel caterpillar arranging and sticking together the leaves of that plant, and spinning underneath them a thin cocoon of white silk (Figs. 119, 120). Some caterpillars make their cocoons on the surface of the earth,

Fig. 120. — Larva of CucuIHa verbasci.

and even with earth. These cocoons are spherical or oblong. Their exterior is more or less well shaped, but their interior is always smooth, polished, shining like moistened earth, v/orked up together into a kind of paste, and carefully smoothed out. This cocoon is besides lined with a covering of silk of variable thickness. The shell is not made of earth alone; threads of silk may be seen in it, crossing each other, and binding together the particles of earth.

These subterranean workers do

not allow their proceedings to be pig. 121. -Cocoon of the Cucullia verbasci easily observed. Reaumur was fortunate enough to be able to notice their skill in the construction .of their shells or cocoons. The Cucullia verbasci (Fig. 120) makes itself a thick and very compact cocoon of the form of an egg (Fig. 121). Reaumur took one of these out of the ground before it is fortified. He tore it partially open, and placed it in a glass vase containing sand, but the poor insect was not long in repairing the disorder caused by the rough hand of our naturalist. It only took four hours to restore its cocoon to its former state.

'' It began," says Reaumur, " by coming almost entirely out, and

left only its hinder part within. It moved its head forwards as far as was necessary to enable it to seize a particle of earth. As soon as it had got its load, it re-entered the interior of the cocoon. It deposited the grain of earth, and came out again immediately, as it did at first, to pick up another grain, which it carried likewise into the interior of the cocoon. This operation it continued for more than an hour. ... The provision of materials being got together, the caterpillar now devoted his whole attention to working them up. It began by spinning over one part of the edges of the opening. After having put over this a small band of very loose web, the caterpillar's head left the opening, the insect went right back again into its cocoon, and the head returned to the opening loaded with a little grain of earth, which it entangled in the silky threads. It then entangled in them two or three, or a greater number of grains, according to the quantity of threads it had spun. It bound them into these with other threads, after which it drew threads over the edges of another part. By thus going round the whole rim of the opening, and by carrying and fixing the grains of earth in the threads which were the last stretched over the opening, it rendered its diameter smaller and smaller." .. It was by working with its head that our mason gave to the new wall of its cocoon the necessary curvature. It was interesting to know how, as it could no longer put out its head, it could stop up the orifice.

" It knew how to change its manoeuvres. Wh^n the opening was reduced to a circle of only a few lines in diameter, it drew threads from a point on the circumference to another on the other side. Thus the opening was covered in with a rather open net-work As soon as this web was finished, it got a grain of earth (which it had laid by until it was wanted), brought it up, placed it against the web, and by pushing and pressing it, made it pass through the web until it reached the exterior, and so in succession the whole of the web was covered with grains of earth.... ". It was not satisfied with rendering the exterior of this place exactly like the rest of the shell; it fortified it thoroughly; it added to it, one after another, layers of grains of earth, till it was as solid and as thick as the rest." The larva of Pyralis corticalis, which is found on oak trees in the month of May, shows to what a point these little insects carry their industry in the construction of their cocoons, in the choice of their materials, in their manner of working them up, and in the forms thfcy cause them to assume. Reaumur one day saw this caterpillar on a small branch, between two triangular appendages (Figs. 122, 123).

LEPIDOPTERA.

This was the beginning of a cocoon. Each triangular blade was composed of a great number of small, thin, rectangular plates, taken

I Figs. 122, 123.— Cocoon of Pyralis corticalis (magnified, proper size § inch).

from the bark of the twig. The caterpillar detached with its jaws asmall band of bark, and fitted it on, and adjusted it with admirableii precision against the edge already formed. It then fixed it securely

with silk threads. Reaumur saw this caterpillar work and erect in this way a large blade during an. hour and a half.

"When one sees," he says,* "an insect which, to construct a cocoon, begins by collecting together an infinite number of small plates of bark in order to compose of them two flat triangular blades; which, to gain its end, takes means that seem so roundabout, although they are the most suitable and the quickest it could adopt, one is very much tempted to consider such an insect, when one sees it thus acting, possessed of reason."

These two blades are at last transformed into a regular cocooi The little animal, which is at the same time architect, cabinet-makei and weaver, arranges it in such a way as to form a hollow cone, whicl

it only remains for it to shut. Re'aumur calls this sort of cocoon orl shell, la cogue en bateau, the boat-shaped cocoon. Some caterpillars weave cocoons of the same form with pure silk.

To bring this subject to an end, we will mention the industry of the Puss Moth (Dicranura vinula), and that of a small Tmea, which eats the barley stored away in our granaries.

The larva of the puss moth employs in the construction of its shell the wood of the tree on which it has lived. It bites it up, and mixing it with a glutinous fluid which it secretes from its mouth, reduces it to a sort of paste, which it then uses in the formation of an envelope, of such hardness that a knife can hardly cut into it.

The Tinea lines the interior of a grain, of which it has previously devoured the contents, with a coating of silk, and divides it thus into two different chambers. In one of these it is to change into a pupa; in the other it places its excrement. And so the little careful architect constructs its house in such a manner as to find in it tranquillity, cleanliness, and comfort.

When caterpillars have not within their reach the materials they are in the habit of employing, like good workmen, they content themselves with what they can get. Re'aumur reared a caterpillar which formed its cocoon of pieces of the paper of which the box was made in which it was imprisoned.

What an extraordinary condition! what a strange phase of vitality does the chrysalis present to us — a being occupying the middle state between the caterpillar and the perfect insect! How little does it resemble that which it previously was, and what it will become! In appearance it is scarcely a living being; it takes no nourishment, and has no digestive organs; can neither walk nor drag itself along, and

• Mem. 12, vol. i., p. 487.

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hardly bends the joints of its body. The outside skin of the chrysalis appears to be cartilaginous; it is generally smooth, although some species have hairs scattered over their bodies.

We distinguish in chrysalides two opposite sides. The one is

the insect's back, the other its under side. On the upper part of the latter (Fig. 124) we perceive various raised portions, formed and arranged like the bands round the heads of mummies; the back is plain and rounded in a great number of pupae; but a great many others have on the upper part, along the edges which separate the two