THE EGGS OF INSECTS. 43 



Ants. It would seem that in these cases the embryo 

 has the power of absorbing oxygen through the 

 shell, which, being of an elastic nature, the creature 

 within is allowed to expand, and the egg, before it 

 is hatched, frequently attains to twice the size which 

 it was when first laid. The eggs of no other class of 

 animals exhibit anything similar to this curious 

 fact, excepting perhaps the spawn of fishes, the 

 growth of which is, however, not of a strictly 

 analogous character. 



The shells of some insect eggs are extremely 

 thick and hard, while others are composed of a 

 mere film. Some of the harder kinds can scarcely 

 be crushed with a knife ; such, for instance, as those 

 intended to brave the inclemency of our winters, 

 while the more delicate are such as are destined to 

 be quickly hatched. These, however, are often so 

 delicate, that without the aid of different kinds of 

 protection afforded by the parent, they would dry 

 up and perish in the course of a single bright sum- 

 mer morning. It may be noted here that there is 

 no calcareous substance contained in the egg-shells 

 of insects similar to that which forms the basis of 

 those of birds. 



The number of eggs laid by a single parent 

 varies to a most extraordinary degree, as a very few 



