I7 2 NORTH AMERICAN DIPTERA. 



41. Third joint antennae oblong, with its apex attenuated, the arista 



bare; scutellum I)ispinose [Spyridopa, S. A.). 

 Third joint subglo1x>se: scntelhun bispinose {Panacris, S. A.) 



42. Upper branch of antennae with a terminal arista and a lateral pro- 



cess. . Neochauna. 



Upper branch with a short, slender style and no lateral process 

 1 Blaslocera, S. A. 1. 



43. The scntelhun terminates in a stout median spine or process (4, 5 1 



Cynipimorpha. 

 Scutellum without median spine or process, simple. . . 44 



44. Third vein with an anterior branch. ..... 45 



Third vein without branch. ..... Zabrachia. 



45. Third antenna] joint oval, with its terminal arista briefly but 



densely plumose Lophoteles. 



Third joint rounded or oval, its terminal arista bare (27). 



Pachyg-aster. 



The relationships of the genera allied to Sazg us 1 Geosargus) —Mero- 

 sargus, Macrosargus {Pedicella Bigot), Chrysoehrpma, Microchrysa 

 and Myiochrysa, are all more or less doubtful. Even Ptecticus can 

 not be sharply limited by the structure of the second antenna! joint. 

 I suspect that Pedicella will have to take precedence over Sargus\ 

 Macrosargus and Geosargus, and that Chrysochroma will have to be 

 merged into Merosargiis. The whole group sadly needs revision. 

 The genus Nothomyia, which I do not know, may perhaps find its 

 proper place under 28. 



