280 THE LIFE OF AN INSECT. 



no door by which it can escape readily, gnaws 

 away the wood until it leaves only an extremely 

 delicate layer between it and the outside of the 

 tree, which is as thin as writing paper. This done, 

 it enters into the pupa state. Its time in that 

 condition being accomplished, it moves itself by 

 the same contrivance as the cossus, and actually 

 pushes through the thin layer, and appears on the 

 outside of the tree, thus making its escape from 

 prison by pushing down a part of its prison 

 wall! 



An instance described by the naturalist Bonnet 

 is yet more ingenious in the arrangements by 

 which the insect escapes. While in the larva form 

 it takes up its abode inside the leaf of an ash, 

 curiously rolled up into a cone ; and then, after a 

 time, it becomes a pupa, forming a silken cocoon of 

 a very slight texture, and, therefore, easily rup- 

 tured by the insect, which it suspends like a ham- 

 mock in the midst of its habitation. It is the 

 closely joined sides of its leafy dwelling that form 

 a barrier which, were it not for the precaution of 

 the larva, would be impenetrable to so small and 

 weak an animal. But, like the last-mentioned, 

 this larva seems to be aware of the feebleness of 



