28 BULLETIN 116, UNITED STATES NyVTIONAL MUSEUM. 



13. Middle basitarsi without a large bristle above No. 2, monticola, new species. 



Middle basitarsi with a large bristle above 14. 



14. Middle basitarsi mostly white or whitish No. 22, sien/iamman Zetterstedt. 



Middle basitarsi black 15. 



15. Antennae and fore coxae wholly black No. 20, corax Osten Sacken. 



First antennal joint yellow below; fore coxae usually conspicuously yellow on the 



whole inner side No. 21, acricola, new species. 



16. Hind margin of wing expanded a little just basally from the tip of the fifth vein, 



so as to form a slight sinus between this point and tip of sixth vein; all tarsi 



wholly black No. 14, detersus Loew. 



Hind margin of wing nearly evenly rounded 17. 



17. Second and third joints of fore tarsi yellowish, first black. . .No. 18, tetricus Loew. 

 Fore tarsi wholly black, or black from the tip of the first joint 18. 



18. Middle basitarsi decidedly yellow at base, sometimes mostly yellow (western 



species) 19. 



Middle tarsi wholly black or nearly so 21 . 



19. Front, occiput, and thorax thickly covered with coarse yellowish pollen, which 



nearly conceals the ground color No. 218, aethiops, new species. 



Front and thorax metallic as usual 20. 



20. Wings with third and fourth veins decidedly convergent at tips. 



No. 10, ovatus Loew. 

 Wings with third and fourth veins only slightly convergent. 



No. 24, acuminatus Loew. 



21. Middle basitarsi more or less yellow at base, usually considerably so; fore tibiae 



more or less tinged with yellow No. 10, ovatus Loew. 



Middle basitarsi wholly black 22. 



22. Bend in last section of fourth vein near its middle; fore tibiae and femora wholly 



black, or very nearly so No. 12, multisetosus, new species. 



Bend in last section of fourth vein considerably before its middle; fore femora 

 and tibiae narrowly yellow at their tips 23. 



23. Bend in last section of fourth vein about the length of the cross vein beyond that 



vein No. 11, myosota Osten Sacken. 



Bend in last section of fourth vein distinctly more than the length of the cross 

 vein beyond that vein No. 8, nigrimanus, new species. 



24 . All the femora more than half black 25. 



One or two pairs of femora yellow on more than distal half . ." 62. 



25. Lower orbital cilia black 26. 



Lower orbital cilia pale 47. 



26. All tibiae black or blackish, except that the middle pair have a white or yellowish 



ring in the middle; their basitarsi mostly whitish. 



No. 22, stenhammari Zetterstedt. 

 At least fore tibiae yellow 27. 



27. Fore tibiae yellowish; middle tibiae black with a yellowish ring occupying their 



middle third, sometimes only base and tip a little infuscated. 



No. 22, stenhammari Zetterstedt. 

 Fore tibiae yellow; middle tibiae black, except that sometimes they are a little 



yellow at tip or at base along upper edge of basal half 28. 



Four anterior tibiae yellow ' - 34. 



28. Middle and hind femora each with two preapical bristles 29. 



Middle and hind femora each with one preapical bristle 31 . 



29. Preapical bristles on middle and hind femora, one before the other, arranged 



longitudinally No. 54, remits, new species. 



Preapical bristles one above the other or nearly so, arranged vertically 30. 



