20 PKOCEEDINGS OF THE NATIONAL MUSEUM vol.83 



Pollen on last three abdominal segments not in defined cross 

 bands, the first pollinose on the sides; mesonotum covered 

 with dense cinereous pollen, the black vittae very distinct 

 behind suture; palpi brownish black; three sternopleurals 

 (Utah) (10) cinerescens, new species. 



8. Front narrowed behind the middle; orbital bristles absent 9. 



Front almost uniform in width to vertex ; one pair of orbitals 



present; arista thickened on proximal tiiree-fourths ; palpi 

 and second antennal segment yellow ; verticals two pairs 

 developed; fourth abdominal segment without discals (Peru). 



(24) armata (Townsend). 



9. Sides of face bare below level of arista outside main row of 



bristles 11. 



Sides of face with hairs extending on lower half outside of 

 parafacial row 10. 



10. Bristles on lower half of face distinctly longer than those 



above and approximating the frontals in size; arista bare, 

 thickened on proximal two-thirds; face strongly receding: 

 palpi dark brown; small cross vein infuscated; epaulets 



black (Mexico, New Mexico) (12) crassiseta, new species. 



Parafacial bristles about equal in length throughout entire 

 row, and less than half the size of frontals ; arista pubes- 

 cent, tliickene<l hardly to middle; palpi pale yellow; abdo- 

 men wholly gray pollinose; wings hyaline; epaulets red 

 (New Mexico) (13) aristalis, new species. 



11. Fourth abdominal segment with discal bristles above 12. 



Fourth abdominal segment without discals above ; first segment 



bearing a pair of median marginals; front about one-half eye 

 width; arista distinctly pubescent (Texas, North Carolina, 

 Guatemala) (IS) apicalis, new species. 



12. First abdominal segment with a pair of median marginal 



bristles; arista pubescent; front narrow, 0.22 of head width; 

 third antennal segment four times length of second 



(Mexico) (20) validinervis (Van der Wulp). 



First abdominal segment without median marginals ; arista 

 bare; front rather wide, about 0.29 of head width; third 

 antennal segment six to seven times longer than second 

 (United States, widespread) (19) affinis, new speciea 



1. Fore tarsal segments compressed and swollen, claws and 



pulvilli minute or atrophied 4. 



Fore tarsal segments ordinary, the claws and pulvilli well 

 developed 2. 



2. Last section of fifth vein one-half as long as preceding section 3. 



Last section of fifth vein about one-third length of preceding 



section ; third antennal segment as wide as parafacial 

 and three times length of second; abdomen thinly gray 

 pollinose, subshining; costal spine longer than small cross 

 vein; wings hyaline (California, Arizona) (6) setigera (Coquillett). 



3. Abdomen shining black, last three segments with pollen in 



defined bands on basal fifth ; palpi pale yellow ; sterno- 

 pleurals, 2; no infrasquamal hairs; small species, length 

 4 mm (Idaho) (7) obliqua, new species. 



