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, orjjn the rich endosperm of the developing seed 

 before it has hardened. 



