SOCIETAL EVOLUTION 1 43 



a manner that certain ones, specialized lor the purpose, 

 secure and distribute nutriment to the whole. The raison 

 d'etre of the society seems to be primarily the facihtation 

 of this function. In other societies, however, Hke those of the 

 social insects (wasps, bees, ants, termites) nutrition seems 

 to be subordinated to producing and rearing as many young 

 as possible, so that reproduction and all that it implies 

 would appear to be the principal adaptive peculiarity of 

 such societies. Among the flocks and herds of birds and 

 mammals, nutrition and reproduction are less conspicuous 

 than the forms of social behavior connected with protection. 

 For discussions of these societies the reader may be referred 

 to the works of Espinas (1924) and Petrucci (1906) and the 

 recent volume of Alverdes (1927). As would be expected, 

 primitive human societies have their closest analogues 

 among certain gregarious mammals, and notably among 

 the anthropoid apes. 



The problem of greatest interest to the student of animal 

 associations and societies is concerned with the precise 

 nature of the communal bonds, or social cohesion which 

 causes the individuals to assemble and remain together for 

 a longer or shorter period. The aggregations in some cases 

 are obviously the result of mere accidental .propinquity 

 due to the individuals hatching simultaneously from a 

 batch of eggs deposited by the mother organism directly 

 on food suitable for the young. Thus the larvae of such 

 insects as the gypsy moth and potato bettle are too feeble 

 to stray far from the egg cluster from which they hatch 

 and really need not stray far from one another because they 

 are surrounded by an abundant supply of nutriment. 

 The same is true of plant lice which are born alive by their 

 feeble wingless mothers and the sluggish, legless larvae 

 of Drosophila and blow flies which hatch from numbers 

 of eggs laid almost simultaneously in fermenting fruit or 

 decomposing flesh. We need not assume, therefore, that 

 such aggregations of larvae are due to fondness for one 

 another's company or are kept together by any other bond 

 than a simple chemotropic response to their common 

 nutritive environment. But some aggregations and associa- 

 tions undoubtedly depend on stimuli emanating from the 



