H2 ANTS. 



hand, and micrcrgate>. or >mall workers, on the other, has been several 

 times repeated in remotely related genera. In some genera (Staiaiiiinit 

 sens, str., f.cptntlinni.v ) there are also indications of a lapsing of 

 highly specialized into simpler conditions by a kind of social degenera- 

 tion. In its extreme form this manifests itself as a suppression of 

 castes and a con.-equent simplification of polymorphism. Beautiful 

 examples of this condition are furnished by the parasitic species that 

 have lost their worker caste. But there are also cases in which the 

 <|iieen ca>te has been suppressed and its functions usurped by workers. 



Not only have these greater changes been effected and fixed during 

 the phylogenetic history of the Formicidse, but also many subtler 

 differences such as those of stature, coloration, pilosity and sculpture. 

 And although such differences belong to the class of fluctuating varia- 

 tions and are usually supposed to have a greater ontogenetic than 

 phylogenetic significance, they are undoubtedly of great antiquity and 

 must therefore be regarded as more important than many of the minor 

 morphological traits. 



Emery was the first to call attention to a number of peculiar phylo- 

 genetic stages in the development of stature among ants ( 1894^). \Ye 

 find by comparison with the male, which may be regarded as a rela- 

 tively stable and conservative form, that the cospecific females and 

 workers may vary in stature independently of each other. The follow- 

 ing are the stages recognized by Emery, with some additions of my 

 own : 



1. In the earliest phylogenetic condition, which is still preserved in 

 the ants of the subfamily Ponerinse and in certain Myrmicinse (Pscitdo- 

 niyrtna, Mynnccina, etc.). the workers are monomorphic and about 

 the same size as the males and females. 



2. The worker becomes highly variable in stature from large forms 

 (dinergates, or maxima workers ) resembling the female, through a 

 series of intermediate (desmergates, mediae) to very small forms 

 (minima workers, or micrergates ). This condition obtains in the 

 Dorylinas, some Myrmicinae (some species of Phcidolc, Phcidologe- 

 ton. .Itta), Camponotime (Camponotus) and Dolichoderinae (Aztcca\. 



3. The worker becomes dimorphic through the disappearance of 

 the desmergates, so that the originally single and highly variable caste 

 is now represented by two. the soldier (dinergate ) and worker proper. 

 "We find this condition in certain Myrmicinse and Camponotinas (Cryp- 

 toccrus, Phcidolc, Acanthomyrmex, Colobopsis, etc.). 



4. The soldier of the preceding stage disappears completely, so that 

 the worker caste again becomes monomorphic but is represented by 

 individuals verv much smaller than the female. Such individuals are 



