THE SOCIAL INSECTS 



the same sort of vegetable food as probably satisfied their 

 solitary ancestors. This was at first made possible by their 

 special relations with the protozoa in their intestines. Similar 

 intestinal inhabitants are known in some solitary, wood- 

 feeding cockroaches. If this specialisation is lost, a more 

 varied diet at once becomes necessary. 



The disadvantages of living by hunting other animals are 

 that the supply is too variable and not really large enough to 

 allow many hunters to live in one place. The driver and 

 legionary ants have carried this type of existence to its extreme 

 development, at the expense of being permanently nomadic. 

 They appear to be a successful sideline from the main stream 

 of ant evolution. Bees and wasps have attained to a different 

 solution. They have never developed any private source of 

 food, but compete with a large number of other animals. 

 It is true that bees and flowering plants have had a profound 

 influence on one another's evolution, but nectaries which 

 are open to bees but closed to other insects are possible 

 only to a limited extent. 



The wasps are still mainly hunters, and only a very few 

 of them, such as a few of the South American Polybiines, 

 compete seriously for nectar. Bees and wasps have, however, 

 developed great powers of flight and an ability to work hard. 

 While honey-bee workers will get their nectar and pollen 

 from near at hand if they can, it is not at all unusual for them 

 to fly 2 miles or even considerably farther. 



It is well known that in man large communities were 

 possible only after agriculture had been developed. This 

 not only provides much more food per acre than hunting 

 does, but also supplies it in a form in which it can be stored 

 for use in winter. The honey bee and the honey-gathering 

 wasps, although not agriculturists, both lay up similar 

 reserves. The termites seem on the whole to manage by 



198 



