"It knew how to change its manoeuvres. When 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 network.... 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 they cause them to assume. Réaumur one day saw this caterpillar on a small branch, between two triangular appendages (Figs. 122, 123). This was the beginning of a cocoon. Each triangular blade was composed of a great number of small, thin, rectangular plates, taken from the bark of the twig. The caterpillar detached with its jaws a small band of bark, and fitted it on, and adjusted it with admirable precision against the edge already formed. It then fixed it securely with silk threads. Réaumur saw this caterpillar work and erect in this way a large blade during an hour and a half. [Illustration: Figs. 122, 123.--Cocoon of Pyralis corticalis (magnified, proper size 2/3 inch).] "When one sees," he says,[39] "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." [39] Mem. 12, vol. i., p. 487. These two blades are at last transformed into a regular cocoon. The little animal, which is at the same time architect, cabinet-maker, and weaver, arranges it in such a way as to form a hollow cone, which it only remains for it to shut. Réaumur calls this sort of cocoon or shell, _la coque 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 _Tinea_, which eats the barley stored away in our granaries.