THE SOCIAL INSECTS 



of this behaviour in the individual ant may be merely hunger 

 or more specifically, need for extra proteins. But the circum- 

 stances of the whole colony for several preceding weeks may 

 have subjected that ant to protein starvation. Over a much 

 longer period it may have been advantageous for the species 

 to develop a habit of egg-eating when the rate of multipli- 

 cation was out of balance with the food supply. In the dis- 

 cussion which follows, many of the arguments are chiefly 

 concerned with the more remote levels. An individual insect 

 may behave in a way which is advantageous to it or to its 

 colony in the long run, without any suggestion that it knows 

 what it is doing. Some behaviour, indeed, such as egg-eating, 

 may seem harmful in the short run. 



REPRODUCTION 



While all species, including man, are capable of rapid 

 multiplication if enough food is available, there are good 

 grounds for thinking that the rate characteristic of each species 

 has been subject to evolutionary change. A species which 

 produces more young will not benefit unless more of them 

 are also brought to maturity. Many marine animals, such as 

 fish or molluscs, produce immense numbers of eggs of which 

 very few survive. In many of these animals the eggs and 

 sperm are merely liberated into the sea, and fertilisation is a 

 haphazard process. A less wasteful method of pairing is a 

 prerequisite of a smaller egg-production. Insects commonly 

 produce a few hundred eggs each, and of these a higher but 

 still small proportion reach maturity. It is advantageous to 

 reduce the number of eggs only if at the same time they have 

 more chance of survival, probably through the development 

 of maternal care. 



Most insects do, in fact, lay their eggs in some more or 

 less protected situation on or near the food which their young 



192 



