THE VAPOURER MOTH 8i 



insects where the females habitually ■ walk or run, both sexes 

 are often incapable of flight. If the female can do no more 

 than walk, walking will suffice for the male too. Whether the 

 parent disperses the eggs, so that the larvse may not be 

 crowded, or whether the young larvae disperse as circumstances 

 require, is a matter of no great consequence. One insect 

 adopts one method, and another another. The responsibility 

 for dispersal may be undertaken by the parent, or by the 

 young, or shared between them. Whatever the larva can do 

 for itself, the female can safely leave undone ; but what the 

 larva cannot do, by reason of sluggishness or restricted diet, 

 the parent must provide for. Hence activity and intelligence 

 in the one tend to degeneration in the other. A sluggish 

 maggot, buried in its food, requires a nimble and quick- 

 witted mother, but an active larva, able to shift for itself 

 under a variety of circumstances, may do well enough, even if 

 the mother is stationary.* 



* Weismann has clearly pointed out the relation between a plentiful 

 supply of food for the larva and the disuse of flight by the parent. See his 

 essay on " Duration of Life." 



