CLASSIFICATION OF ANIMAL AGGREGATIONS 31 



peckers, are given as examples. Obviously, such a category is with- 

 out secure foundation, but is perhaps to be expected from a worker 

 who beheves that the future belongs, however the present resists, to 

 the psychic and not to the mechanistic (Deegener, 19206). 



II. Heterosymporia are mixed migration societies, such as occur in 

 birds and mammals, and are especially well marked on the plains of 

 South Africa. 



Beta. Irreciprocal societies occur when the benefits extend mainly 

 to one species, while the other may be decidedly harmed from the 

 association. 



1. Synclopia, or thieving societies, are those in which one species 

 feeds upon the stored food supplies of another, as thieving ants are 

 known to prey upon stored termite food, or as thieving species of 

 termites take the food of other termites. Wheeler calls this clepto- 

 hiosis; Forel designates it as lestohiosis. 



2. Syllestia are societies containing robber guests which prey upon 

 the eggs or the young of the species with which they are associated. 

 Thus staphylinid beetles may prey upon the brood of the ant colonies 

 whose nests they inhabit, as Wheeler's "synechthren." In somewhat 

 similar relations are the hawks that prey upon flocks of migrating 

 birds. The flocks of wandering grasshoppers, springbok, and the like 

 are each set upon by its own particular set of predators which ac- 

 companies the food flock on its migrations. 



3. Paraphagia are societies composed of harmless companions of 

 their host feeding commensually on fragments neglected by the 

 host. Alcippe, a boring barnacle, inhabits the snail shells which have 

 been appropriated by hermit crabs, and feeds on fragments escaping 

 from the feeding of the latter. Dermestid beetles occupy nests of 

 other insects, feeding on waste material such as molted skins. The 

 so-called synoektes of ants form paraphagia with the ants with which 

 they live. 



4. Synoeciiim is the term given by Deegener to the association be- 

 tween certain animals and the nests of other animals. This is known 

 to be a widespread relationship. The crab Pinnixa hves in holes oc- 

 cupied by marine mollusks. Birds' nests have m.any animals regular- 

 ly living in them; sparrows may build in storks' nests. Fishes build in 



