1916] Wheeler — An Anomalous Blind Worker Ant 145 



since many such peculiarities are merely suppressions or absences 

 of structures that are well developed in the males and females of 

 the same species. I doubt, however, whether we are justified in 

 drawing such a sweeping conclusion in the face of numerous facts 

 which indicate even more forcibly that the worker characters 

 have arisen from continuous and fluctuating variations. In many 

 genera of ants with polymorphic workers {Camponotus Pheidole, 

 etc.) and in many genera containing numerous species, though 

 with monomorphic workers (Solenopsis, Monomorium, etc.) the 

 eyes show a gradual or serial diminution. Discontinuity may, 

 therefore, be conceived to arise in the development of these struc- 

 tures by a selective survival of certain stages or phases, just as it 

 does in the series of species or of dimorphic workers of the same 

 species. The absence of wings is another character in worker 

 ants which is sometimes supposed to have arisen as a mutation, 

 but, though very rare, anomalous workers with vestigial wings 

 (pterergates) are known to occur. I have recorded and figured 

 such cases in Myrmica and Cryptocerus, and others have been ob- 

 served in the former genus by Wasmann and Donisthorpe. 

 Recently I have found an even more instructive case, an Australian 

 Monomorium, allied to M. rothsteini Forel, the normal females of 

 which have very small wings, too small to be of any service as 

 organs of flight. These females, which will be described and fig- 

 ured in a future paper, are, in fact, truly brachypterous, like cer- 

 tain well-known species of Diptera, parasitic Hymenoptera, Hete- 

 roptera and Orthoptera, and suggest that the complete loss of 

 wings in the worker is merely the final stage in a gradual diminu- 

 tion of these organs and has, therefore, originated from continuous 

 variations. As the worker phase of the ants must have been per- 

 fected and fixed as a family character not later than the Eocene 

 Tertiary and probably as early as the Cretaceous, it is not sur- 

 prising that at the present time organs characterizing stages inter- 

 mediate between the workers and females should be so rarely 

 resuscitated as anomalies. 



