THE SOCIAL INSECTS 



human variation in stature and in colour of hair and skin 

 are not related to social duties. With the requisite training, 

 most men can do most of the essential work of the com- 

 munity. 



To return to insect societies, clearly the fundamental 

 problem of their origin is, " How did physiological differ- 

 ences arise within the species ? " Solitary bees and wasps 

 construct nests, and only a slight lengthening of the life of 

 the mother would be enough to make it overlap those of her 

 offspring. They are also capable of producing exclusively 

 female broods, though none of the solitary species is known 

 to do this except occasionally by chance. Such Hymenoptera, 

 therefore, could at once set up a primitive society of the 

 Halictus or Polistes type if they could produce a brood of 

 young females who would work without laying eggs. 



There is little doubt that an important factor has been the 

 modifying influence which social life has on the process of 

 natural selection. In a solitary species, individuals with 

 reduced fertility will not often survive in competition with 

 others which are more fertile. But in social species any 

 change which benefits the group as a whole is likely to be 

 preserved. 



In insects generally a reduction in size of the female is 

 nearly always associated with the laying of a smaller number 

 of eggs. It is significant that in most species the worker is 

 smaller than the queen. It is possible that originally, as is 

 still true to some extent, queens and workers differed chiefly 

 because of chance variations in the amount of food which 

 they received as larvae. Later, a system could have been 

 evolved in which differences in the food received had a greater 

 effect on the adult, whereas in solitary species the tendency 

 would be to keep the species as insensitive as possible to 

 variations in food supply. When physiological studies have 



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