CASE OF BARK-SKIN. 203 



In order to give a sufficient degree of strength to 

 their cocoons, some larvae adopt the plan of form- 

 ing them partly of silken fibre and partly of other 

 materials. Reaumur, being on an entomological 

 excursion in the forest of Vincennes on a fine day 

 in the month of May, fell in with a most curious 

 cocoon, formed by a larva which feeds upon the 

 oak-tree. At first he could scarcely conceive 

 what the object he saw before him was, but on 

 removing the branch it proved to be a very singu- 

 lar cocoon. Detaching a small branch, on which 

 was a larva just commencing its cocoon, Reaumur, 

 finding the evening draw on, set out on his return 

 home. The larva did not seem to discover the 

 fact of its being carried away a prisoner ; and as the 

 entomologist carried the branch with gentleness, 

 it proceeded with its task as comfortably as if 

 stationed on the tree it was now leaving behind. 

 Reaumur beguiled the tedium of the way by 

 carefully watching its mode of proceeding in the 

 formation of its cocoon. He thus noticed the 

 larva cutting very delicate layers of the fine upper 

 skin or epidermis of the bark of the twig, which it 

 fastened together by silken cords, and then formed 

 into two wing-like pieces fastened on each side of 



