Among caterpillars that make a very slight cocoon, some, as the Catocalas, gather together two or three leaves into a ball, to protect them. Others strengthen their cocoons, and render them opaque by adding earth or other substances, often obtained from their own bodies. Some, after having spun their cocoon, cast forth through the anus three or four masses of a matter resembling paste, which they apply with their head to the inside of the cocoon, and which, drying quickly, becomes pulverulent. Others employ for the same purpose the hairs with which their bodies are covered.
The larva of Acronycta aceris ([Fig. 113]) is covered with tufts of yellow hair. Réaumur made these caterpillars work under his own eye in glass vases. They make the layer which is to form the exterior surface of their shell, or cocoon, of pure silk, and when it is thick enough, tear out their hair, now from one place, now from another. But we will leave the illustrious observer to relate this operation himself, which must without doubt be painful to the poor animal:—
Fig. 112.—Larvæ of Catocala fraxini.
Fig. 113.—Larva of Acronycta aceris.
