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 
