4 i2 ELEMENTARY ZOOLOGY 



bees stand first. As already explained (see pp. 22O et seq), 

 there are among these communal insects several different 

 kinds of individuals in each species. With most animals 

 there are two kinds only, males and females, which may 

 or may not show differences in color, form, etc., so that 

 they are readily distinguishable. Among all the com- 

 munal insects, however, there are always three kinds of 

 individuals, males, females, and workers, these last being 

 infertile individuals. With the social wasps and social 

 bees the workers are all infertile females and are smaller 

 than the fertile forms; with the termites there are 

 besides the fertile males and females, which are winged, 

 workers which are wingless, and also peculiar wingless 

 individuals called soldiers which have very large jaws and 

 whose business it is to fight off attacking enemies of 

 the community. Among the ants the workers are also 

 wingless, while the males and females are winged. The 

 worker ants in many species are of two kinds, socalled 

 worker majors and worker minors, differing markedly in 

 size. All the ant workers are good soldiers, but with 

 some the fighting is done almost wholly by certain 

 especially large-headed and large-jawed ones which may 

 be called soldier-workers. 



Thus among all strictly communal animals there is a 

 specialization or differentiation of individuals accompany- 

 ing the division of labor. Special individuals have a 

 certain part of the work of the community to do, and they 

 are specially modified in structure to do this work. This 

 structural modification may make them incapable of per- 

 forming certain other labor or work w r hich is necessary 

 for their living and which must be done for them, therefore, 

 by others. Thus the mutual interdependence of the in- 

 dividuals composing a colony is very real. The worker 

 honey-bees cannot perpetuate the species; honey-bees 

 would die out were it not for the males and females. But 



