AGGREGATIONS OF ANIMALS 107 



Unlike ants, these young catfishes readily accept 

 strange minnows of their own species into their 

 group even though they may be markedly differ- 

 ent in size. This means that they form an open 

 society as contrasted with the social organization 

 of the ant family. 



With ants the recognition of other members of 

 the family-colony is usually by a contact-odor 

 sense. Many ants are totally blind and even 

 those with eyes frequently live in totally dark 

 places. For all such it appears that theirs is a 

 world of odor-shapes and spaces, just as ours is a 

 world of color forms. Ants will attack and kill 

 another that lacks the colony odor to which they 

 are accustomed. The ants appear to learn which 

 odor to accept, for observations have shown that 

 if newly emerged, so-called callow ants are placed 

 together, though they come from different species 

 as well as from different colonies, and if for the 

 first few days of their adult life, each is made to 

 touch every other member of the artificially mixed 

 colony with her antennae at least once a day, 

 then this group will form a new unit and will 

 attack outsiders that lack the nest odor to which 

 they have become accustomed. 



Relatively unorganized aggregations occur in 

 nature most frequently as over-wintering col- 

 lections; thus snakes collect in the autumn in 



