12 BULLETIN 116, UNITED STATES NATIONAL MUSEUM. 



12. Hind basitarsi with ten or twelve large bristles (California; Colorado). • 



No. 12 multisetosus, new species. 

 Hind basitarsi with only two to si.x large bristles lli. 



13. Hypopygial lamellae brown or brownish 14. 



Hypopygial lamellae white with a black border 15. 



14. Face narrow, silvery white (Illinois) No. 1, calainus Melander and Brues. 



Face very wide, whitish; hypopygium and their lamellae rather small (Idaho). 



No. 4, sordidatus, new species. 



15. Lamellae of the hypopygium acutely pointed at tip (Eastern States). 



No. 24, acuminatus Loew. 

 Lamellae not acutely pointed at tip 10. 



16. Hypopygial lamellae large, rather subquadrate in outline (Colorado). 



No. 15, enigma Melander and Brues. 

 Hj'popygial lamellae shaped otherwise 17. 



17. Lamellae of the hypopygium oval 19. 



Hypopygial lamellae somwehat triangular in outline 18. 



18. Lamellae small and cut off rather straight at apex; fore tarsi wholly black 



(western) No. 11, myosota Osten Sacken. 



Lamellae of moderate size, more rounded at apex 20. 



19. Hypopygial lamellae not at all jagged at apex (California). 



No. 5,formosus, new species. 

 Lamellae jagged on apical margin 20. 



20. Fore tarsi scarcely as long as their tibae, slightly yellow at base; second, third, 



and fourth joints of nearly equal length (New York; Wisconsin; Idaho). 



No. 10, ovatus Loew. 

 Fore tarsi a little longer than their tibae, wholly black; second joint longer than 

 third, and more than twice as long as fourth (Idaho). 



No. 8, nigrimanus, new species. 



Group D. 



1. Costa greatly enlarged before the tip of first vein; middle tarsi very long and 



slender, each joint distinctly enlarged at tip; face reaching below the eyes 



(Nevada; Utah) No. 33, appendiculatus, new species. 



Not with the above combination of characters 2. 



2. Cilia of the calypters pale 3. 



CiHa of the calypters black 10. 



3. Wings marked with black or brownish 4, 



Wings grayish hyaline, or only slightly clouded along the front 5 



4. Wing^s clouded with brown in front and along the veins; last three joints of 



hind tarsi fringed above (Puget Sound; N. Europe). .No. 50, remipes Wahlberg. 

 Apex of the wing with a conspicuous black or brown spot (Eastern States). 



No. 48, setifer Loew. 



5. Front covered with white pollen, which, viewed in certain directions, con- 



ceals the ground color (Massachusetts). .No. 28, agronomus Melander and Brues. 

 Front metallic, more or less shining ' 6. 



6. First antennal joint unusually long and rather slender (Alaska). 



No. 64, humilis, new species. 

 First antennal joint normal 7. 



7. Hind tibiae distinctly thickened, mostly black 8. 



Hind tibiae rather slender, yellow with black tips 9. 



8. Middle and hind femora black at base, mostly yellow, the latter without 



ciliS below, but with a fringe of long hairs on upper inner edge (Washington; 

 California) No. 56, californicus, new species. 



