– Wings without spots, transparent, monochromatic or regularly darkened in anterior half ... 13

4. Wings with numerous brownish-yellow-spots in anterior half; fore femur with 6-7 strong spines in basal part; 2.3-2.7.Fig. 72 ... nebulosus Fallén

– Wings with 2 spots on a posterior transversal vein m-cu and on M₁₊₂ flexure ... 5

5. Fore femur at apex with a small lobe, excavation and bunch of setae; IV sternite with a light spot; fore coxae with black hairs ... 6

– Fore femur at apex without an excavation and lobe ... 7

6. Epistome mostly silvery-white, with small spot under antennae; acrostichal setae short; fore femur with short ventral hairs; proepisteron with white hairs; 3.5-5.0.Fig. 61 ... albiceps Frey

– Epistome mostly metallic-green, with weak dusting in inferior part; the acrostichal setae are longer; fore femur with longer hairs; proepisteron mainly with black hairs; 4.2-5.4.Fig. 71 ... signifer Coquillett

7. The fore tibia are clearly squeezed and are strongly bent; legs with long hairs; 4.1-5.2.Fig. 80 ... rogenhoferi Mik

– Fore tibia cylindrical, straight ... 8

8. Epistome metallic brilliant, green; fore femur with one row of strong setae in basal part; 3.6-5.2.Fig. 64 ... bipunctatus (Lehmann)

– Epistome without metal shine ... 9

9. Clypeus silvery-white ... 10

– Clypeus with dark-coloured dusting ... 12

10. Halter with a dark spot at apex, epandrial lobe at apex almost straight; 3.5-5.4.Fig. 65 ... borealis Loew

– Halter yellow ... 11

11. Fore femur with long whitish anteroventral setae equal in length to diameter of femur; clypeus silvery-white, epistome with a metallic-green spot under antennae; 3.6-4.4.Fig. 73... norvegicus Ringdahl

– Fore femur without long whitish anteroventral seta in apical half; face with whitish-grey tinge; 2.9-3.9.Fig. 77 ... rufibarbis Gerstäcker

12. Leg without long hairs; halter dark; 3.8-4.4.Fig. 69 ... geminus Frey

– Midtibia with long hairs exceeding in length diameter of tibia, halter usually light with dark knob; 3.2-4.8.Fig. 76... pilipes Frey

13. Fore coxae with black hairs and setae in apical part; face metallic-green; fore tibia with triangular widening on apex; 2.8-3.1.Fig. 62... alpinus Wahlberg

– Fore coxae with light hairs ... 14

14. Clypeus and most part of epistome monochromatic ... 15

– Face dichromatic: the colouring of epistome strongly differs from colouring of clypeus ... 20

15. Fore femur at apex with flat scale-like setae ... 16

– Fore femur without flat setae ... 17 

16. Fore femur with one ventral row of setae; 2.5-4.2.Fig. 70... litoreus Fallén

– Fore femur with two rows of setae or with irregular sparse setae; surstylus bent ventrad at apex; 3.3-4.0.Fig. 68... freyi Storå

17. Fore tibia at apex with acute ventral tooth; wings with yellow veins at base; 2.2-4.7.Figs. 81, 82 (1-5) ... praecox (Lehmann)

– Fore tibia at apex without the tooth ... 18

18. Face silvery-white or light grey ... 19

– Face ochre-yellow; 3.3-4.2.Fig. 78... viridis (Meigen)

19. Halter at apex dark; genae high; 5.0... albosignatus Ringdahl

– Halter yellow; genae small; 3.7-4.1. Fig. 75... pectinatus Gerstäcker

20. Wings with weak yellow-brown darkening at vein m-cu; fore femur with long ventral setae; 2.6-3.2.Fig. 66... brunnicosus Loew

– Vein m-cu without yellow-brown darkening ... 21

21. Halter dark; 4.1-5.2.Fig. 79... altivagusAldrich

– Halter yellow ... 22

22. The lateral lobe of surstylus widened at apex; hypandrium triangular; 2.3-3.4.Fig. 63... balticus (Meigen)

– Lateral lobe of surstylus narrow; hypandrium bandlike; 2.6-3.5.Fig. 67... callostomus Loew

23. Scutellum with 2 setae ... oceanus (Macquart)

– Scutellum with 4 setae ... 24

24. Wings with dark spots ... 25

– Wings without spots, transparent, monochromatic or irregularly darkened in anterior half ... 34

25. Wings with numerous brownish-yellow spots in anterior half; face rusty-yellow ... nebulosus Fallén

– Wings with 2 spots on posterior transversal vein m-cu and on M₁₊₂ flexure ... 26 

26. Fore coxae with black hairs and setae in apical part ... 27

– Fore coxae with light hairs ... 28

27. Proepisteron, as a rule, with dark hairs; acrostichal setae long; fore femur with long hairs; apical sternite with oval emargination ... signifer Coquillett

– Proepisteron, as a rule, with white hairs; acrostichal seta short; fore femur with short hairs; apical sternite with cuneiform emargination ... albiceps Frey

28. The epistome is bright metallic shining, clypeus brownish pollinose; halter dark ... bipunctatus (Lehmann)

– Epistome without metallic shine ... 29

29. Femora with long hairs; hairs at least on midfemur are almost equal in length to diameter of femur ... 30

– Femora with short hairs; their length does not exceed diameter of femora ... 31

30. Legs with long hairs, their length clearly exceeds width of podomeres, for example on mid femur; wing with distinct limb in anterior half... rogenhoferi Mik

– Legs with shorter hairs, their length does not exceed diameter of femora; wings are almost imperceptibly darkened in anterior half ... pilipes Frey

31. Halter yellow ... 32

– Halter at least partially dark ... 33

32. Fore femur with bunch of anteroventral hairs in apical third, equal in length to half or one third of diameter of fore femur ... norvegicus Ringdahl

– Fore femur with short hairs ... rufibarbis Gerstäcker

33. The sternite of an apical segment is cut deeply out; the emargination at apex is rounded; halter knob yellow with yellowish-brown spot ... borealis Loew

– The sternite of an apical segment is cut shallowly out; the emargination is pointed at apex; the halter knob at apex not yellow-brown ... geminus Frey

34. Fore coxae with dark hairs ... alpinus Wahlberg

– Fore coxae mostly with light hairs ... 35

35. The epistome is bright metallic shining ... 36

– Epistome dim or pollinose ... 37

36. The apical sternite of an oviscapt is cut deeply out, styli of an oviscapt nearly globular ... balticus (Meigen)

– Apical sternite of an oviscapt wide, with small oval emargination ... callostomus Loew

37. Face light (grey or yellowish) ... 38

– Face dark (metallic-green) ... 43

39. Fore tibia at apex with acute ventral tooth; wings at base with yellow veins ... praecox (Lehmann)

– Fore tibia at apex without the tooth ... 40

40. Wings in the basal part with yellow veins ... pectinatus Gerstäcker

– Wings with dark veins ... 41

41. Abdomen with light dorsal hairs ... viridis (Meigen)

– Abdomen with dark dorsal hairs ... 42

42. Epistome under antennae with a spot ... freyi Storå

– Epistome under antennae without a spot ... litoreus Fallén

43. m-cu with yellowish-brown spot ... brunnicosus Loew

– m-cu without yellowish-brown spot ... 44

44. Fore femur with setae in the basal 1/2 only ... albosignatus Ringdahl

– Fore femur with setae in the basal 2/3 with dark ... altivagusAldrich