Fig. 117.—Larva of Chelonia caja forming its cocoon.
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. Réaumur 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 with its head, to lay the hairs along the interior surface, and to keep them down by threads, which it draws over them. At another time Réaumur 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 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 light white web. This web supports the hairs, causing the greater part of them to curve at their upper extremity, in such a manner as to form a sort of cradle.
| Fig. 118.—Small Caterpillar of the Pimpernel. | Fig. 119.—Cocoon of the same. |
It remains for us now to speak of the caterpillars that make their cocoons of silk, together with other materials. Réaumur saw the Pimpernel caterpillar arranging and sticking together the leaves of that plant, and spinning underneath them a thin cocoon of white silk ([Fig. 119]).
Fig. 120.—Larva of Cucullia verbasci.
Some caterpillars make their cocoons on the surface of the earth, 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, worked 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.