THE SOCIAL INSECTS 



inhabitants of any member of their family. It is not yet 

 possible to say whether their solution of the problem of 

 food-supply has enabled them to make other cultural 

 advances. Our knowledge of their behaviour is still in a 

 rudimentary state. 



The general conclusion is that social insects have increased 

 the variety of their diet, that is they use a greater proportion 

 of what is available near at hand. Apparently very few have 

 been able to increase the quantity of any one kind to be found 

 within reach of the nest. It is possible that some of the ants 

 which keep cattle have done so, and it is almost certain that 

 the leaf-cutter ants have solved this problem. 



THE ORIGIN OF SOCIAL BEHAVIOUR 



The third point to be considered is the acquirement of 

 social behaviour by species which were originally solitary. 

 This also involves the idea of division of labour, and ulti- 

 mately the question of communication. 



The simplest example of the division of labour is seen 

 where two sexes share the duties of reproduction. There is a 

 number of animals which show us that such a division need 

 not be made. In many molluscs, such as our common land- 

 snails, every individual performs the function of both sexes. 

 Nevertheless, in the great majority of species the sexes are 

 separate. This applies to almost all insects, and to all verte- 

 brates. 



It is characteristic of insect societies that the division of 

 labour amongst their members is founded chiefly on physical 

 differences which are often well marked. Apart from 

 differences in behaviour which depend upon age, all the 

 individuals which have distinct roles in the society differ 

 from one another in structure. The differences between the 

 queen and the worker, between the soldier, the worker major 



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