THE ANIMAL KINGDOM. 



149 



and of an external layer, formed of dense hairs laid on like 

 the slates of a roof, and forming an impermeable cloth. 

 Thus the young brood are doubly protected : against the 

 severity of winter's cold, and against its destructive rains. 



Some kinds of gall-insects, still more devoted to their off- 

 spring, immolate themselves in order to protect them. As 

 the enormously distended insect gradually expels its eggs, 



77. Pine Silk- Worm Moth (Bombyx dispar): Caterpillar, Chrysalis, and Butterfly, male and 



female. 



it heaps them up in a little pile, and when its body is quite 

 cleared out, so that it resembles a hollow bladder, the fe- 

 male straightway covers her progeny with it, attaches the 

 edges round them, and dies directly after ; thus forming for 

 them a convex, solid roof, the impermeability of which pro- 

 tects the eggs against the injurious agency of the air and 



