2. Males: hypopygium present ... 3

– Females: hypopygium absent ... 14

3. Scutellum haired ... 4

– Scutellum bare, without hairs ... 7

4. Mesonotum entirely covered with hairs in addition to setae; abdomen silvery pollinose, with yellow transparent spots laterally; 6.0-8.0 ... diaphana (Fabricius)

– Only anterior part of mesonotum covered with hairs in addition to setae ... 5

5. Femora black; usually 2^nd tergite of abdomen only with yellow lateral spot; 5.5 ... subarctica Ringdahl

– Femora yellow; hind femur with black apex; usually 2^nd and 3^rd abdominal tergites with yellow spots laterally ... 6

6. Mesonotum and abdomen without silvery white pollination; antennal stylus shorter than antennomeres combined; frons greyish-white; face white; 6.0-7.0 ... magnicornis (Zetterstedt)

– Mesonotum and abdomen metallic green, densely silvery white pollinose; antennal stylus longer than antennomeres combined; frons and face silvery-white; femora mostly yellow; 6.0-7.0 ... setimana Loew

7. Mesonotum silvery white pollinose (anterior view) ... 8

– Mesonotum metallic brilliant, without silvery white pollination ... 11

8. Face and frons silvery white pollinose (anterior view) ... 9

– Face and frons black (anterior view) ... 10

9. Antennal postpedicel twice longer (along lower margin) than high at base; antennal stylus shorter than antennomeres combined; femora yellow except for brownish apical part of hind femur; 5.0-5.5 ... argentina (Meigen)

– Antennal postpedicel 1.5 times longer (along lower margin) than high at base; antennal stylus longer than antennomeres combined; femora usually dark; rarely femora yellow with apical part of hind femur blackish; 5.0-7.0 ... argyria (Meigen)

10. Antennal postpedicel 1.5 times longer than high at base; femora usually dark with anterior four femora yellow at apex; rarely femora yellow with apical part of hind femur blackish; (see above) ... argyria (Meigen)

– Antennal postpedicel not longer than high; femora yellow; fore femur in basal half and hind femur in distal half black; 6.0-8.0.Fig. 12 ... leucocephala (Meigen)

11. Frons and face white or greyish-white (anterior view) ... 12

– Frons and face black (anterior view) ... 13

12. Hind basitarsus longer than next segment of tarsus; abdominal segment VIII without strong setae; abdomen metallic green, brilliant, with weak silvery-white pollination laterally; 2^nd and 3^rd tergites with yellow lateral spots; femora and tibiae yellow; hind femur and hind tibia at apex darkened; 6.0.Fig. 11 ... spoliata Kowarz

– Hind basitarsus equal to or shorter than next segment of tarsus; 8^th abdominal segment with strong setae; abdomen metallic green; 2^nd to 4^th tergites usually with yellow lateral spots; femora and tibiae yellow; hind femur at apex darkened; 4.5-5.0 ... elongata (Zetterstedt)

13. Hind basitarsus with one long ventral seta at base; anterior four femora yellow; hind femur black in apical part; at least 2^nd tergite with yellow spot laterally; 5.0 ... ilonae Gosseries

– Hind basitarsus without ventral seta; all femora black; abdomen metallic green; 5.0 ... auricollis (Meigen)

14. Scutellum haired ... 15

– Scutellum bare, without hairs ... 16

15. Mesonotum entirely covered with hairs in addition to setae ... diaphana (Fabricius)

– Only anterior part of mesonotum covered with hairs in addition to setae ...magnicornis (Zetterstedt) and setimana Loew

16. Antenna longer than head; R₁ shortened; antennal pedicel haired dorsally ... elongata (Zetterstedt)

– Antenna as long as or shorter than head; R₁ joining costa at approximately middistance between humeral transversal vein and apex of R₂₊₃; pedicel bare dorsally ... 17

17. Hind basitarsus longer than next segment of tarsus ... 18

– Hind basitarsus at most equal to next segment of tarsus ... 19

18. Hind coxa entirely black ... auricollis (Meigen)

– Hind coxa more or less yellow ... ilonae Gosseries

19. Hind coxa yellow at apex ... argentina (Meigen)

– Hind coxa entirely black ... 20

20. Lower calypter with black to brown cilia ... leucocephala (Meigen)

– Lower calypter with brownish to yellow cilia ... argyria (Meigen)