262 THE SOCIAL LIFE OF ANIMALS 



the Store of sperm which she received in the nuptial 

 flight the same female can allow her eggs to be fer- 

 tilized; such fertilized eggs become females. 



We have seen the comparative unimportance of 

 the males. Although the active colony is usually 

 composed of females only, these may be quite dif- 

 ferent in appearance and function. Typically there 

 are the reproductive females and the sterile ones. 

 Among the ants the sterile females are divided into 

 the protective soldiers, whose main function is to 

 protect the colony from the attack of other species 

 of animals, and the workers proper. The ant work- 

 ers are subdivided on the basis of size (Figure 48). 



Professor Wheeler made the study of these social 

 insects, particularly the ants, his life work. In a 

 small book, published in 1937 after his death, he 

 reaffirmed his belief that ants and bees have evolved 

 from ancestral wasps, and that each has developed 

 the caste system independently. (124) 



With bees and wasps, whether a given fertilized 

 egg is to produce a worker or a sexual "queen," bet- 

 ter called a reproductive female, depends on the 

 treatment and food which is given to the grub 

 which hatches from the egg. If she receives plenty 

 of food and is given space in which to grow she 

 becomes fully matured sexually; if fed less and kept 

 more crowded she becomes an incomplete female 



