SOCIAL EVOLUTION AS A BIOLOGICAL PROCESS 263 



these potential queens or princesses in special roomy 

 cells apart from the ordinary brood chambers; one of 

 them soon emerges to become a new sovereign. Let us 

 note in passing how similar this is to the production of 

 new egg-cells in a Hydra, when the mature germs of an 

 earUer generation are prepared and discharged. When, 

 now, the colder weather sets in, and the possibility of 

 subsequent swarming is set aside, the reigning queen is 

 allowed by her attendant guards to visit the royal cells, 

 whose occupants she stings to death, thus destroy- 

 ing any possible claimant to her place. And when the 

 royal princess constructs her part of the pupal case, 

 she leaves an aperture so that if and when it should 

 become necessary for the queen to kill her, the sovereign 

 would not injure her sting and be unable to kill the other 

 individuals who might become aspirants for the throne 

 and so precipitate a civil war ! As in the case of the 

 self-destructive act on the part of a stinging cell in 

 Hydra, altruistic subservience to the interests of the 

 colony can go no farther. 



The ants form stable colonies of still higher grades, 

 where the workers are not all alike in general structure, 

 but become more rigidly specialized for the performance 

 of restricted tasks. As before, there is the fundamental 

 differentiation into the sexual "queens" and males, and 

 the sterile workers concerned with the immediate 

 material life of the community. In some species the 

 workers serve as herdsmen, caring for the ant-cattle or 

 aphids, from which they receive minute drops of a 

 sweet juice for food. The aphids are tended on the 

 leaves of various plants during the summer, and are 

 carefully reared and stabled and fed below ground during 



