34 ANIMAL AGGREGATIONS 



which, to be sure, are only partially closed communities (Schjel- 

 derup-Ebbe, 1922, 1923). In the open societies membership is much 

 less exclusive, and chance alone determines whether or not its mem- 

 bers shall unite or separate. The open societies may be organized, 

 like those of the saiga antelopes, which have guards and leaders; or 

 unorganized, as in many groupings of what Alverdes regards as, 

 strictly speaking, non-social insects, as when grasshoppers, butter- 

 flies, caterpillars, and the like unite in migrating swarms. 



CLASSIFICATION OF ESPINAS AND WHEELER 



Wheeler, in his discussion of animal societies (1930), gives a sum- 

 marized scheme of classification of social and subsocial groupings, 

 based upon the work of Espinas, which is reproduced herewith in a 

 somewhat modified form. The principal modifications made have 

 been the placing of all distinctions between homotypic and hetero- 

 typic groupings in the third and least important column, the re- 

 arranging of the categories under associations, and the substitution 

 of "anthropoid" for "human" in the last category. Wheeler does not 

 believe that the societies arose from associations, although he says 

 that the ancient aggregative or associative proclivities may have 

 been retained by many species and may serve to reinforce their 

 specifically social behavior. This subject will receive more detailed 

 attention in the last two chapters. 



CLASSIFICATION ON BASIS OF INTEGRATION 



It is illuminating to attempt a classification of social grouping on 

 the basis of the type or the degree of integration of the social group. 

 Some of the available knowledge on this point will be set forth later. 

 From many points of view this seems a most desirable basis of 

 classification, but there is not at present sufficient exact knowledge 

 to justify an elaborate attempt in this direction. When made, such a 

 classification would follow the general outlines suggested by Deege- 

 ner, at least to the extent that such a scheme would present the 

 social organization of animals from the loosely organized, apparently 

 chance aggregations due to collections around favorable locations or 

 on account of physical limitations which prevent separation, through 



