THE CANADIAN ENTOMOLOGIST 273 



10. Thorax with ihree pairs of postsutural dorsocentral bristles: mid tibia 



with one or two bristles on anteroventral and posteroventral 



surfaces melanderi Malloch. 



Thorax with four pairs of postsutural dorsocentral bristles 11. 



11. Halteres and calyptrit yellow; mid femur with a conspicuous group of 



dense, stiff, obtusely pointed bristles on apical third of anteroventral 

 and ventral surfaces, and a series of about 8 very long, strong bristles 

 extending from base to beyond middle of posteroventral 

 surface johnsoni Mall och . 



Halteres black or dark brown, calyptrae whitish; mid femur not armed as 

 above 12. 



12. Second, third and fourth segments of mid tarsus with a fringe of very fine 



hairs along posteroventral margin; mouth-margin very much produced; 

 arista with very short pubescence ; hind tibia with a series of erect setulose 

 hairs on anterodorsal surface, one or two of which are longer than the 

 others, the hairs of entire series at least as long as the diameter of 

 tibia siihrostratus Zetterstedt. 



Mid tarsus without hairs as above; mouth-margin not produced 13. 



13. Hind tibia without strong bristles on anterodorsal surface, the hairlike 



bristles on anteroventral surface much longer than the posterodorsal 

 bristles, which number from five to seven; fore tibia with dense, moder- 

 ately long hairs on ventral surfaces; mid tibia with a number of bristly 

 hairs of irregular lengths on apical half of ventral 

 surface villicnirus Coquillett. 



Hind tibia w^ith two long bristles on anterodorsal surface, the antero- 

 ventral bristles not longer than those on the posterodorsal surface... 14. 



14. Mid tarsus distinctly shorter than mid tibia; longest hairs on arista about 



twice as long as its basal diameter; abdomen with a broad black triangle 

 on dorsal segments 2 and 3; preapical dorsal bristle on hind tibia 

 stron g breviiarsis Mall och . 



Mid tarsus distinctly longer than mid tibia; longest hairs on arista about 

 as long as its basal diameter; abdomen with the black dorsal marks on 

 segments 2 and 3 nearly linear; preapical dorsal bristle on hind tibia 

 weak or absent mnociiiis Zetterstedt. 



FEMALES. 



1. Thorax and abdomen yellow diaphaniis Wiedemann. 



Thorax and abdomen black 2. 



2. Abdomen with paired dorsal spots; hind tibia without posterodorsal 



bristles; thorax with three pairs of postsutural dorsocentral 



bristles maculiveniris Malloch. 



Abdomen wathout paired dorsal spots 3. 



