246 NORTH AMERICAN DIPTERA 



KEY TO GENERA 



1. Discal cell closed 2 



Discal cell open apically the venation incomplete (3) Chalarus Walker 



2. Scutellar bristles present 3 



Scutellar bristles absent (1, 2) Pipunculus Latreille 



3. Ocellar bristles absent; occiput widely visible from the side (6, 7). 



Nephrocerus Zetterstedt 

 Ocellar bristles present; occiput narrow (4, 5) Verrallia Mik 



Pipunculidse. — 1, 2, Pipunculus; 3, Chalarus; 4, 5, Verrallia; 6, 7, Nephrocerus. 



