Chapter II 

 THE LIFE-HISTORY OF INSECTS 



Nature ... by the water's side, 



Out of the mud drew creeping things, 



And, smiling on them, gave them radiant wings. 



J. H. EwiNG. 



The Egg. — Having sketched the main features of 

 the structure of insects, we have next to consider the 

 process of growth by which the complex organs of 

 the adult are built up. These organs are, as we 

 have seen, composed of cells or of substances due to 

 the energy of cells. And the innumerable cells in 

 the body of a cockroach, a moth or a bee, have 

 arisen by the division of the egg-cell laid by the 

 mother. The life-story of any insect, therefore, must 

 begin with the egg. 



The Cockroach's egg has already been briefly de- 

 scribed. It is of elongate shape, like a crescent with 

 rounded ends, one face being convex and the other 

 concave, and of a flattened oval form in cross-section. 

 It is surrounded by a hard outer chitinous coat 

 {chormi) and a thin inner yolk (vitelline) membrane. 

 The interior is filled with protoplasm charged with 

 coarse granules of the food-yolk which nourishes the 

 growing embryo. Just within the yolk-membrane 

 is a thin layer of clear protoplasm. Easily visible 

 while the egg is still in the ovarian tube, but hidden 

 by the accumulated yolk-granules after laying, is the 

 nucleus of the egg-cell — the germinal vesicle, which 



