280 



INSECT ARCHITECTURE. 



than the beauty of its colours, and has consequently at- 

 tracted the attention of every Entomologist. The cater- 

 pillar feeds on fruit-trees and on the willow, and spins a 

 cocoon, in the form of a Florence flask, of strong silk, so 

 thickly woven that it appears almost like damask or 

 leather. It differs from most other cocoons in not being 

 closed at the upper or smaller end, which terminates in a 

 narrow circular aperture, formed by the convergence of 

 little bundles of silk, gummed together, and almost as 

 elastic as whalebone. In consequence of all these termi- 

 nating in needle-shaped points, the entrance of depredators 

 is guarded against, upon the principle which prevents the 

 escape of a mouse from a wire trap. The insect, however, 

 not contented with this protection, constructs another in 

 form of a canopy or dome, within the external aperture, so 

 as effectually to shield the chrysalis from danger. V\e have 

 formerly remarked (page 167) that the caterpillar of the 

 jEgeria asiliformis of Stephens in a similar way did not 

 appear to be contented with a covering of thin wood, with- 

 out an additional bonnet of brown wax. The cocoon of the 



Cocoons of tlie Emperor-moth, cut open to show tlien- structure. 



emperor-moth, though thus in some measure impenetrable 

 from without, is readily opened from within ; and when 

 the moth issues from its pupa case, it easily makes its way 

 out without either the acid or eye-files ascribed to the silk- 

 worm. The elastic silk gives way upon being pushed from 



