SOCIAL LIFE 237 



Among ants all the species are social, and members of 

 the worker caste are sharply differentiated by complete 

 winglessness ; while they show the highly developed 

 structural features of their order, with modifications fitting 

 them for the specialised activities of their lives, wings are 

 never developed in the course of their transformation. 

 Hence the worker-ants are more strongly differentiated 

 from their fertile sisters than worker wasps and bees are ; 

 and in many groups there may be recognised, among the 

 wingless infertile females, two or more distinct forms 

 divergent from each other in size and often in structure, 

 while among the fertile females (queens) as well as the males, 

 separate castes may in some cases be distinguished. The 

 winglessness of worker-ants is matched by the females of 

 many non-social Hymenoptera, species of gallflies and 

 members of groups with parasitic larvae, for example. 

 Among the ScoHoids, believed by Wheeler and others to 

 represent the ancestral stock of true ants, there are two small 

 famiHes — the Thynnidae and Mutillidae — whose females 

 are wingless. It seems, therefore, that this condition may 

 have arisen independently in a number of groups among 

 the Hymenoptera, and that it has become a fixed character 

 among all the ant workers. It is suggestive to remember 

 that in the workers of certain species of ant, vestiges of 

 wings may occasionally be detected. Quite a number of 

 abnormal forms of queens tending to resemble workers 

 and also forms of worker more or less resembling queens 

 have been described and provided with special names for 

 which reference may be made to Wheeler's book (1910). 

 Some of these worker- like ('* ergatoid ") queens are wingless 

 like the workers. It is well known that all ant- queens after 

 the nuptial flight shed their wings ; only by the persistent 

 bases of these can the queen in a nest be recognised as an 

 insect once able to rise in the air. The flight-muscles of 

 the wingless queen, now no longer required, undergo a 

 rapid degenerative process described in detail by C. Janet 

 (1907). These muscles, " the most voluminous of all the 

 organs of the body, experience a precocious senescence," 



