282 THE LIFE OF AN INSECT. 



pupa within from the invasion of enemies from 

 without. 



Upon the pear or willow tree may sometimes 

 be found an illustration of escape from the pupa, 

 altogether well deserving our notice. In such 

 situations the brown flask-shaped cocoon of the 

 emperor moth may occasionally be discovered. In 

 structure it is composed of a solid tissue of layers 

 of silk, almost of the texture of parchment ; but 

 at the narrow end, or that which may be compared 

 to the neck of the flask, it is composed of a series 

 of loosely attached longitudinal threads, converg- 

 ing like so many bristles to a blunt point, in the 

 middle of which is a circular opening, through 

 which the moth makes its escape, the threads 

 readily yielding to pressure from 

 within, and acting somewhat on the 

 principle of the wires of the opening 

 to a rat-trap, or the willow cricks of 

 an eel-trap. The silk of its cocoon 

 is of so strong a texture, and so 

 closely gummed, that had both ends 



Cocoon of Emperor , 1111,1 n 



Moth. been similarly closed, the egress of 

 the insect would have been impracticable. But, 

 it may be thought, such a cocoon is exposed 



