Key to species of the subgenus Geron Meigen from the Nearctic Region

1. Wing hyaline ................................................................................................................. 2

­. Wing slightly infumate.................................................................................................. 3

2. Crossvein r­m at middle of cell dm; scape with black hairs; basicostal pile pale yellow ....................................................................................................... subauratus Painter

­. Crossvein r­m beyond middle of cell dm; scape with brown hairs; basicostal pile white ............................................................................................................ johnsoni Painter

3. Crossvein m­cu straight or nearly so (Fig. 27) ............................................................. 4

­. Crossvein m­cu sinuous (Fig. 28) ............................................................................... 6

4. Front of female with white to silver scales medially; crossvein r­m at middle of cell dm; oral margin with come cinereous color................................................................. 5

­. Front of female with golden scales medially, silver scales restricted to eye margins; crossvein r­m beyond middle of cell dm; oral margin pure white .................................. ................................................................................. stenos Hall & Evenhuis, sp. nov.

5. Scutellum completely devoid of scales; oral margin grayish white; vaginal furca (Fig. 20) with lateral struts angled outward .............. prosopidis Hall & Evenhuis, sp. nov.

­. Scutellum with a few white scales at anterolateral corners; oral margin gray; vaginal furca (Fig. 8) with lateral struts angled inward apically ................................................. ............................................................................... elachys Hall & Evenhuis, sp. nov.

6. Front of female with silver to white scales medially ................................................... 7

­. Front of female with golden scales medially ............................................................. 13

7. Mid tibia of male yellow to orange; crossvein r­m at or beyond middle of cell dm..... 8

­. Mid tibia of male black to brown; crossvein r­m beyond middle of cell dm ............ 10

8. Crossvein r­m beyond middle of cell dm ..................................................................... 9

­. Crossvein r­m at middle of cell dm...................... painteri Hall & Evenhuis, sp. nov.

9. Front of female with yellow medial spot above oral margin; fore tarsi of female with unmodified setae ............................................. nevadensis Hall & Evenhuis, sp. nov.

­. Front of female without yellow medial spot above oral margin; fore tarsi of female with specialized palynophilic setae spatulate apically (cf. Fig. 29) (best seen under high magnification) ...................................................................... holosericeus Walker

10. Male scutellum with scales, some specimens with a few restricted to anterolateral corners .......................................................................... albipilosus Hall & Evenhuis, sp. nov.

­. Male scutellum devoid of scales ................................................................................ 11

11. Upper occiput and dorsum or thorax and abdomen with golden scales admixed with silver to white scales ....................................................................... albidipennis Loew

­. Upper occiput and dorsum of thorax and abdomen with white scales........................ 12

12. Vaginal furca with broad lateral struts with ends turned up (Fig. 5) .............................. .............................................................................. borealis Hall & Evenhuis, sp. nov.

­. Vaginal furca with lateral struts narrow, ends not turned upward (Fig. 4)...................... ............................................................................................................. argutus Painter

13. Mid tibia of male brown to black ............................................................................... 14

­. Mid tibia of male orange to yellowish ........................................................................ 20

14. Crossvein r­m at middle of cell dm............................................................................. 15

­. Crossvein r­m beyond middle of cell dm .................................................................... 16

15. Pile of occiput all white; vaginal furca with lateral struts club­like apically (Fig. 9) .... ........................................................................... eriogonae Hall & Evenhuis, sp. nov.

­. Pile of occiput yellowish above, white below; vaginal furca with lateral struts broad apically, curved inward (Fig. 12) ..................... infrequens Hall & Evenhuis, sp. nov.

16. Male scutellum with scales ................................................................... niveus Cresson

­. Male scutellum devoid of scales ................................................................................. 17

17. Fore tarsi of female with spatulate palynophilic setae (Fig. 29); oral margin pale col­ ored, yellowish to cinereous....................................................................................... 18

­. Fore tarsi of female without palynophilic setae; oral margin darker than above, orange­ yellow in color................................................... monticola Hall & Evenhuis, sp. nov.

18. Basicostal hairs and scales yellow to golden ............................................................. 19

­. Basicostal hairs and scales silvery white.............. cressoni Hall & Evenhuis, sp. nov.

19. Mid leg of male black; male katepisternum dense white pilose and tomentose, pleura cinereous pollinose; female meron silvery pilose and tomentose; vaginal furca with apex of lateral struts containing long, thin inward process (Fig. 19) .............................. ................................................................................ peucon Hall & Evenhuis, sp. nov.

­. Mid leg of male brown; male katepisternum sparse white pilose, pleura generally dull gray, not pollinose; female meron bare; vaginal furca with apex of lateral struts containing broad, rounded inward process (Fig. 10) ................... halli Evenhuis, sp. nov.

20. Antennal scape with black hairs................................................................................. 21

­. Antennal scape with white hairs (a few black hairs may be present apically)........... 23

21. Crossvein r­m at middle of cell dm; male scutellum with yellow scales........................ .......................................................................................................... senilis (Fabricius)

­. Crossvein r­m beyond middle of cell dm; male scutellum devoid of scales.............. 22

22. Basicostal hairs and scales whitish; female fore tarsi with spatulate palynophilic setae (Fig. 29) usually restricted to apical tarsal segments; vaginal furca with lateral struts very broad, not twisted (Fig. 21) ..................................................... rufipes Macquart

­. Basicostal hairs and scales golden; female fore tarsi without palynophilic setae; vaginal furca with lateral struts thin, twisted (Fig. 25) ............................ vitripennis Loew

23. Basicostal hairs and scales yellow; male scutellum with scattered yellow tomentum 24

­. Basicostal hairs and scales white; male scutellum with or without tomentum .......... 25

24. Crossvein r­m at middle of cell dm; oral margin pale yellow; vaginal furca with apex of lateral struts complex, consisting of three connected plates (Fig. 16) ....................... .................................................................................. notios Hall & Evenhuis, sp. nov.

­. Crossvein r­m beyond middle of cell dm; oral margin brownish; vaginal furca with apex of lateral struts with one inwardly and one outwardly directed lobe (Fig. 26)....... ............................................................................... weemsi Hall & Evenhuis, sp. nov.

25. Crossvein r­m at middle of cell dm................................................... parvidus Painter

­. Crossvein r­m beyond middle of cell dm ................................................................... 26

26. Oral margin cinereous to whitish ........................................................ nigripes Painter

­. Oral margin orangeish to yellow orange .................................................................... 27

27. Vaginal furca with pointed protuberances on inner margin (Fig. 3); distal ends of lateral struts not recurved inward ........................................................... arenicola Painter

­. Vaginal furca without such protuberances on inner margin; distal ends of lateral struts recurved inward (Fig. 6)...................................... confusus Hall & Evenhuis, sp. nov.