348 GENERAL BIOLOGY 



is more or less proportionate to the extent of the changes} 

 to be made during transformation. The advantage of this 

 lies in the ability of such an insect to avail itself of a rich 

 but transient food supply. A generation may be reared 



FIG. 200. Adult and nymph of the mayfly Calli- 

 baetis skokiana (drawn by Miss Maude H. 

 Anthony). 



on the fallen carcass or the ripe fruit before it is decom- 

 posed, or in the rich endosperm of the developing seed 

 before it has hardened. 



