— I '2 — 



On the Classification of North American Diptera. 



(Third paper. Concluded from p. 1 16 ante. ) 

 By Dr. S. \Y. Williston. 

 BERIDINAE. 

 Abdomen with seven visible segments in the male, in the fe- 

 male with an additional ovipositor. Wings with a stigmatic spot; 

 all the posterior veins arise from the discal cell.* Abdomen flattened. 



1. — Three posterior veins; occiput fiat 2 



Four posterior veins; scutellum with spines 3 



2. —Scutellum with spines; palpi rudimentary Beris Latr. 



Scutellum without spines (Metbponia L\v., non Macq.). Allognosta O.S. 



3. — Occiput excavated; hind femora thickened at the extremity * Neoexaireta O.S. 



Occiput flat, hind femora simple; last two abdominal segments small 



Scoliopelta, n. g. 

 SARGINAE. 



Body usually elongate; rather small, nearly bare species. Four 

 posterior veins, the last one arising from the basal cell. Antenna? short, 

 the third joint rounded or subquadrate, with an apical or pre-apical 

 arista. Scutellum without spines on its border. (Occiput deeply ex- 

 cavated. ) 

 1. — Anterior ocellus more widely separated than the other two; males holoptic or 



dichoptic . . . # 2 



(Ocelli equidistant, more approximate 3 



2. — Abdomen contracted toward the base, clavate or pedicillate 



Macrosargus Bigot. 

 Abdomen not pedicillate in the male, in the female the second segment not con- 

 cave on the sides Sargus, Fabr. 



3. --Second antennal joint prolonged on its inner side into a projection, extending on, 



and closely lying upon, the third joint Ptecticus Loew. 



Second joint not with such a projection 4 



4. — Males dichoptic; eyes bare Chrysonotus Loew. 



Males holoptic; posterior veins weak 5 



5. — Eyes thickly pilose *Chloromyia Dune. 



Eyes bare, deep metallic species; front very broad in the female; arista terminal; 



abdomen short; eyes of male with an area of enlarged facets above 



Microchrysa Loew. 

 STRATIOMYINAE. 



Rather large species, the abdomen usually oval and more or less 

 thickened. Five posterior cells; often, however, one or more of the three 

 veins that arise from the discal cell are faint or entirely rudimentary, and 

 the cells hence coalescent: in these cases, the discal cell will usually show 

 angulations, indicating the origin of such veins. The last posterior vein 



* This character I have found variable in species of Beris; its precise value in 

 some other genera is yet to be decided. 



