128 CONTROLLED NATURAL SELECTION 



live together in flocks, is not attained some- 

 times for several years. 



Males, when at the zenith of their power, 

 become monarchs of the herd for a season or 

 two, and are then thrown out to die. Poor 

 males never become monarchs. The per- 

 centage of males cannot be dangerously 

 reduced by these methods, because the per- 

 centage of males to females at birth remains 

 always the same. 



In certain species of insects, especially in 

 the Hymenoptera, another kind of society is 

 found, composed of males, females, young and 

 neuters or asexual females. In these societies, 

 the actual production of males is controlled 

 by the females and neuters ; males are pro- 

 duced only when required, and after they have 

 fertilised the young females they either die or 

 are destroyed, the females and neuters alone 

 remaining to carry on the species. (The males 

 of these insects are not provided with weapons 

 of offence stings, &c.) Here, then, pro- 

 visions are made not only for the destruction 

 of males but for the limitation of their pro- 

 duction. 



Asexual reproduction in invertebrates, 

 which is by no means rare, appears to be 



