102 ANIMAL LIFE AND SOCIAL GROWTH 



been estimated to contain 3,000,000 termite in- 

 habitants, to say nothing of the numerous and 

 frequently curiously modified insects that live with 

 them in the same colony. 



Such collections of animals must be considered 

 in analyzing the larger communities of which they 

 are parts. They also have significance in that 

 they furnish transition stages between the loose 

 community organization of which we have been 

 speaking in previous chapters and the more 

 closely knit social life which men and other highly 

 social animals exemplify. 



These aggregations of animals may be chance 

 collections piled up by the waves as are those in 

 the animal drift along Lake Michigan's shore 

 line; as such they may be almost lacking in organ- 

 ization other than that of habitat and food web 

 and the like which characterize the general 

 ecological communities; or they may be actively 

 brought together by the reactions of the animals 

 to light, heat or food or to some other stimulus 

 which serves to collect them in large numbers in a 

 restricted area where conditions are favorable; 

 or finally, they may collect as a result of positive 

 reactions to each other, a sort of social drive 

 which may be inherited along with body color or 

 length of legs and if so is usually regarded as an 

 expression of instinctive or in-born behavior. 



