10 BULLETIN 116, UNITED STATES NATIONAL MUSEUM. 



5. Hind femora yellow except dorsal and part of ventral edge (Idaho). 



No. 63, opportunus, new species. 

 Hind femora black, the tip may be yellow 6. 



6. Fore femora mostly yellow (E. States; Canada). ..No. 67, Jlavilacertus, new species. 

 Fore femora largely black, at least black at base for nearly half their length. . 7. 



7. Fourth joint of middle tarsi distinctly compressed (New York; Illinois). 



No. 54, rernus, new species. 

 All tarsi plain 8. 



8. Hind tibiae wholly black (New Jersey) No. 26, demissus, new species. 



Hind tibiae with basal portion yellow 9. 



9. Middle femora distinctly blackened at base 11. 



Middle femora not, or but slightly infuscated at base 10. 



10. Face ochraceous (Greenland; Labrador) No. 52, groenlandicus Zetterstedt. 



Face silvery (Wisconsin; New York) No. 53, incongruus Wheeler. 



11. Middle and hind femora each with two preapical bristles; third antennal joint 



about one and a half times as long as wide (Idaho). 



No. 38, bisetosus, new species. 

 Middle and hind femora each with one preapical bristle; third antennal joint two 

 or thioe times as long as wide (New York; Massachusetts). 



No. 55, adultus, new series. 



12. Anterior tibiae black or blackish 13. 



Anterior tibiae yellow or yello^vish brown 20. 



13. Last joint of fore tarsi compressed 14. 



Fore tarsi plain 16. 



14. Fifth joint of fore tarsi obcordate, second and third joints usually yellowish 



(Colorado; New Mexico) No. 19, vmnicula, new species. 



Fore tarsi wholly black, fifth joint not notched at tip 15. 



15. First antennal joint yellow below; fifth joint of fore tarsi cut off rather straight 



at tip (California) No. 21, acricola, new species. 



Antennae wholly black; fifth joint of fore tarsi extended a little at upper edge 

 (California) No. 20, corax Osten Sacken. 



16. Middle basitarsi wholly black .' 18. 



Middle basitarsi mostly white 17. 



17. Wings with a conspicuous blackish spot near the tip (Washington). 



No. 23, argentipes, new species. 

 Wings without any trace of such a spot (Alaska; Labrador; North Europe). 



No. 22, stenhammari Zetterstedt. 



18. Hind femora ciliated on lower inner edge (California; Oregon), 



No. 17, paluster Melander and Brues. 

 Hind femora without cilia 19. 



19. Lamellae of the hypopygium blackish (Colorado). .No. 3, barbaricus, new species 

 Lamellae whitish with a black border (Washington; British Columbia). 



No. 2, monticola, new species. 



20. Hind tibiae distinctly yellow for more than one-third their length, at least on 



one side 21. 



Hind tibiae infuscated, at most a little yellow at base 27. 



21. Third antennal joint about three times as long as wide; arista subapical; lamellae 



of hypopygium blackish (Illinois) No. 39, intentus Melander and Brues. 



Third antennal joint not over one and a half times as long as wide; arista dorsal; 

 lamellae whitish 22. 



22. Costa with a long, tapering enlargement at tip of first vein (Eastern States). 



No. 29, gratus Loew. 

 Costa without an enlargement at tip of first vein 23. 



23. Hind femora ciliated below 24. 



Hind femora without cilia 26. 



