20 BULLETIN 116, UNITED STATES NATIONAL MUSEUM. 



51. Hind tibiae scarcely blackened on outer side, but distinctly so on inner surface; 



fore tibiae slightly infuscated at tip, and wdth a few flattened brietles (east- 

 ern) No. 127, pu(jil Loew. 



Hind tibiae sharply black at tip for one-fifth their length or more; fore tibiae 

 wholly yellow and with their hairs and bristles normal (Eastern States). 



No. 124, vigilans Aldrich. 



52. Middle basitarsi laterally fringed (\\idespread) No. 128, plumipes Scopoli. 



Middle basitarsi plain 53. 



53. Hind femora ciliated below with long black hairs ; front usually blue or violet. . 54. 

 Hind femora ■nathout cilia below; front green 55. 



54. Last section of fourth vein bent at a right angle, and \\-ith a stump-vein at pos- 



terior bend ; hypopygial lamellae somewhat triangular, fringed with rather short 

 hairs (Eastern States, from New York to Florida; Kansas). 



No. 114, refledus Aldrich. 

 Last section of fourth vein moderately bent, without a stump-vein; lamellae 

 somewhat orbicular, fringed with very long hairs (eastern). 



No. 113, 7narginatus Aldrich. 



55. Antennae yellow, blackened at tip of third joint; hind tibiae mostly blackish, 



the black shading into yellow at their base (New York). 



No. 112, abrasus, new species. 



Third antennal joint wholly black; hind tibiae only slightly infuscated at tip 



(New Mexico) •. No. Ill, dorsalis, new species. 



Group H. 



1. First antennal joint wholly yellow 2. 



Antennae black, first joint sometimes yellow below, at least narrowly so. . . . 24. 



2. Arista enlarged at tip; wings with a conspicuous lobe at tip of sixth vein 3. 



Arista plain '. . . . 4. 



3. Hypopygial lamellae large; hind margin of wing with a deep sinus before th(; 



lobe (Washington) No. 109, hastatus Loew. 



Lamellae small; hind margin of wing nearly normal, except for the lobe at tip of 

 sixth vein (California) No. 110, comptus, new species. 



4. Fore tarsi ornamented 5. 



Fore tarsi plain 18. 



5. Hind femora ciliated below; fore tibiae slightly enlarged and a little blackened 



at tip (eastern) No. 127, pugil Loew. 



Not with the above combination of characters 6. 



6. Hind coxae yellow; front and dorsum of thorax pollinose, nearly opaque (wide- 



spread; Mexico) No. 126, bifractus Loew. 



Hind coxae more or less black at base; front and dorsum of thorax shining.. . 7. 



7 Wings with a projecting lobe at tip of sixth vein 8. 



Wings without or with scarcely a trace of such a lobe 12. 



8. Wings with the lobe at tip of sixth vein very prominent 9. 



Lobe at tip of sixth vein small 10. 



9. Hypopygial lamellae with the apical margin evenly rounded; costa not enlarged 



at junction of first vein (widespread) No. 155, lobatus Loew. 



Apical margin of lamellae emarginate; costa enlarged at junction of first vein, 



tapering to the tip (widespread) No. 156, omnivagus, new species. 



10. First and second joints of fore tarsi of about equal length (Colorado; Wyoming). 



No. 152, xratus, new species. 

 Second joint of fore tarsi distinctly shorter than first 11. 



