108 THE CANADIAN ENTOMOLOGIST 



9. Arista pubescent; calyptrae with black margins. . . .fuscomarginata Malloch 



— Arista plumose; calyptrae entirely pale.... Hcbecnema resfcrtina Fallen 



10. Arista plumose; prealar bristle absent or minute; mid tibia without antero- 



dorsal bristles Hchccncma iinibratica Meigen 



— Arista pubescent; prealar bristle more than half as long as the one behind 



it; mid tibia with one or two anterodorsal bristles, .tuhcrcitlata Malloch 



11. Thorax with four pairs of postsutural dorsocentral bristles 12. 



- — Thorax with three pairs of postsutural dorsocentral bristles 



12. \"entral surface of scutellum with some soft erect hairs at ai)ex ; mid tibia 



with several anterodorsal bristles brci'i^ Stein 



— Ventral surface of scutellum bare 13. 



13. Mid tibia with an anterodorsal bristle ; mid and hind femora in part black- 



ened dupUcata Meigen 



— Mid tibia without an anterodorsal bristle; mid and hind femora not black- 



ened 14. 



14. Thorax with a very strong pair of presutural acrostichals. .orbifasrfa Stein 



— Thorax without a strong pair of presutural acrostichals. ... rM//V/7?za Stein 



15. Abdomen checkered, without distinct paired dorsal spots; palpi black. . . . 16. 



— Abdomen with paired dorsal black or brown spots, if the spots are indistinct 



the ground colour of the abdomen and sometimes of the thorax is more 

 or less testaceous and the palpi are entirely or largely yellow 17. 



16. Antennae entirely black iniinctica Malloch 



— Third antennal segment consjjicuously reddish yellow at 



base johusoni Malloch 



17. Longest hairs on arista about as long as width of third antennal 



segment Hcbecnema fiili'a Bigot 



— Arista much shorter haired 18. 



18. Hind tibia with one anterodorsal bristle ; abdomen black, densely gray 



pruinescent. with black paired dorsal spots ; pal])i broadly infuscated 

 at apices iiniseta Stein 



— Hind tibia with two anterodorsal bristles ; abdomen more or less testaceous, 



gray pruinescent, with poorly defined brown paired si)ots on dorsum; 

 palpi entirely yellow lysinoc Walker 



19. Scutellum with a conspicuous black spot on each side at 



base idiijinosa Fallen 



— Scutellum without such spots 20. 



20. Third wing-vein with a few weak setulae at base above and 



below X enomydaca buccata Malloch 



— Third wing-vein bare at base 21. 



21. Wings with the cross-veins very conspicuously infuscated ; hir.d til)ia with- 



out posterodorsal setulae near base 22. 



— Wings with the cross-veins not or but slightly infuscated. or the hind tibia 



has one or more posterodorsal setulae near base 24. 



22. Thorax entirely yellowish testaceous ; head and abdoinen fuscous ; arista 



with its longest hairs distinctly shorter than width of third antennal 

 segment bicolorata Malloch 



