270 NORTH amp:rican diptera 



KEY TO AMERICAN GENERA 



1. Ocelli absent 2 



Ocelli present (Chile) Teretrura Bigot 



2. Third antennal segment as large as the second 3 



Third antennal segment minute, the arista curved over the second seg- 

 ment and with long rays on the free side (British Guiana) (1-4). 



Tauroscypson Curran 



3. Alula very narrow 4 



Alula large, convex behind (5) Pyrgota Wiedemann 



4. Apex of anal cell transverse' (Type: Pyrgota chagnoni Johnson). 



Pyrgotella, n. g. 

 Apex of anal cell with triangular production behind (Bolivia). 



Leptopyrgota Hendel 



