292 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1940 



case for apparently crows and other birds post more than one sentinel 

 to watch for danger. If we could understand what is being said 

 by crows in some of their gatherings, or by many other animals, we 

 might learn of discussions and announcements that would surprise 

 us. Certainly these gatherings have every appearance of definite 

 meetings and discussions. 



Some bats live in colonies and others live almost singly. With the 

 exception of the fruit bats, those that live in colonies probably do so 

 because of necessity arising from their habit of passing the daylight 

 hours in caves or crevices, the supply of which is limited. When 

 feeding, they travel widely through the air and work as individuals, 

 probably with no serious competition in capturing their insect prey. 



The fruit bats (family Pteropidae) live mainly in colonies that 

 lead almost a nomadic life, shifting from one region to another to 

 obtain an adequate supply of suitable food. Since there is usually 

 enough food for all, they can live in large groups provided they go 

 where fruit is plentiful. 



The colonial habits of insects, wherein, as among the wasps, bees, 

 and ants, numerous individuals work together to build a common 

 house and to rear the young, form an apparently perfect community. 

 The queen ant who lays the eggs but is helpless to defend herself 

 is guarded continuously by others of her kind that bear scarcely any 

 resemblance to her in appearance because they are remarkably modi- 

 fied for fighting. They are the soldiers of the group. The workers 

 of the ant colony show no evidence of sexual characteristics but are 

 specialized to do the labor for the community. Apparently they 

 have rather definitely assigned duties. Some will forage for food 

 and bring it home ; others will attend to the growing of certain food 

 supplies on which they may feed; others care for the young. In- 

 deed there may be a far greater division of labor among the colony 

 than is generally supposed. 



The recognition of property and territorial rights among animals 

 is clearly evident in many instances. This fact is well known among 

 ornithologists, who have observed that most birds that do not nest 

 in colonies select a nesting site and fight away other individuals of 

 their own species for a rather definite area around the nest., The 

 size of this area, of course, varies with different species, but is fairly 

 constant for each species. This system is obviously based on the fact 

 that any given area will, on the average, produce only a certain 

 amount of food of the kind that is required by the occupants of the 

 area. Therefore, if other pairs were permitted to invade the terri- 

 tory there would be too keen a competition for food. Frequently, 

 other species are tolerated within the nesting area but this is ordi- 

 .uarily because tlie .other species are sufficiently different in their food 



