– Antennal stylus bare, rarely pubescent; notopleuron usually without purple spot; cercus various ... 4

3. Wing at apex with strongly pronounced milky-white spot; antenna black; 6.0-7.0 ... nobilitatus (Linnaeus)

– Wing at apex without milky-white spot; antenna partly yellow; 4.5-6.0 ... infuscatus (Stannius)

4. Metapleuron with group of hairs before posterior spiracle; posterior part of mesonotum and scutellum dorsally with hairs; R₄₊₅ and M₁₊₂ parallel ... 5

– Metapleuron and posterior part of mesonotum usually bare; scutellum usually without dorsal hairs; R₄₊₅ and M₁₊₂ usually convergent ... 13

5. Femora mainly dark, at most yellow on extreme apex ... 6

– Femora mainly yellow, at most infuscated on posterodorsal side ... 7

6. Midtibia swollen, somewhat curved and armed ventrally with 3-4 short spine-like setae which arise from small tubercles; ventral side of midtibia without pubescence; costa conspicuously thickened beyond the end of subcosta; hind tibia completely yellow; larger species, total wing length more than 3.5 ... cupreus (Fallén)

– Midtibia simple, bearing normal pubescence and 1 anteroventral seta; costa not thickened as above; hind tibia distinctly infuscated on apex; smaller species, total wing length less than 3.5 ... angustifrons (Staeger)

7. Fore tibia with 1 conspicuous apicoventral seta; 3.7-4.5 ... chalybeus (Wiedemann)

– Fore tibia without apicoventral seta ... 8

8. Wing with costa strongly thickened between humeral crossvein and tip of subcosta ... 9

– Above section of costa not thickened, distinctly thinner than next section ... 10

9. Cercus yellow; hind basitarsus yellow in proximal half; hind tibia yellow, at most slightly infuscated in apical fifth; costal thickening 2/3 as long as costal cell; 3.0 ... celer (Meigen)

– Cercus brownish-black; hind basitarsus mostly entirely dark; hind tibia slightly to distinctly infuscated in apical fifth; costal thickening 1/3 as long as costal cell; 2.5... brevicornis (Staeger)

10. Face velvet-black; clypeus with short black pubescence; wings clear; cercus distinctly black, well-developed; 2.5-3.0.Figs. 45, 47 ... aerosus (Fallén)

– Face silvery white; clypeus entirely bare; wings distinctly dark; cercus either brownish black or yellow ... 11

11. Proximal part of CuA₁ more than twice longer than apical part; proximal part of M₁₊₂ slightly longer than apical part; cercus well-developed, somewhat round, piceous except for ochreous yellow base; larger species, total wing length on average more than 4.0.Fig. 46, 50... metallicus (Stannius)

– Proximal part of CuA₁ less than twice longer than apical part; proximal part of M₁₊₂ slightly shorter than apical part; cercus rather small; smaller species, total wing length less than 4.0... 12

12. Cercus ochreous yellow; fore coxa mostly yellow, especially on lateral side; femora and tibiae entirely yellow; tarsi only feebly infuscated; 2.5-3.0.Fig. 49 ... blankaartensis Pollet

– Cercus black; fore coxa mostly dark; femora pale yellow; hind tibia slightly to distinctly infuscated in apical 1/4 to 1/3; 2.5-3.0.Fig. 48 ... assimilis (Staeger)

13. Femora yellow ... 14

– Femora black ... 23

14. Lower postocular setae black ... 15

– Lower postocular setae light (white or yellow) ... 17

15. 3^rd and 4^th segment of fore tarsus dilated; 3.0-3.5.Fig. 54. ... chetifer (Walker)

– Fore tarsus simple ... 16

16. Fore tibia bearing long apicoventral seta; 3.7-4.5.Fig. 52 ... chalybeus (Wiedemann)

– Fore tibia without long apicoventral seta; 2.0.Fig. 57 ... nanus (Macquart)

17. Antenna partly yellow ... 18

– Antenna entirely black ... 20

18. Lower calypter with black cilia; first two segments of fore tarsus with white and black rings; cercus trapezoidal, black-brown; 4.0-4.5.Fig. 51 ... chrysosygos (Wiedemann)

– Lower calypter with light (white or yellow) cilia ... 19

19. Antennal postpedicel 1.5 times longer than high; cercus triangular, without distal emargination, half as long as hypopygium, black-brown, yellow at base, with long yellow cilia; 2.5-3.5.Fig. 55 ... fulvicaudis (Walker)

– Antennal postpedicel hardly longer than high; cercus very small, triangular, with shallow distal emargination, 1/4 as long as hypopygium, yellow, black along distal margin, with black cilia; 2.5-3.0.Fig. 58 ... rothi (Zetterstedt)

20. Lower calypter with light (white or yellow) cilia ... 21

– Lower calypter with black cilia ... 22

21. Fore tibia bearing long apicoventral seta; costa thickened at R₁; 4.0-4.5 ... gracilis (Stannius)

– Fore tibia without long apicoventral seta; costa simple; 3.0 ... ruficauda (Zetterstedt)

22. At least 4^th segment of fore tarsus dilated, black; 5^th segment of same tarsus white at apex; 3.0-3.5 ... chetifer (Walker)

– Fore tarsus simple; 3.0-3.5.Fig. 53 ... germanus (Wiedemann)

23. Lower postocular setae black; legs entirely black ... 24

– Lower postocular setae light (white or yellow) ... 25

24. Fore tibia bearing long apicoventral seta; frons whitish pollinose; cercus short but broad; 5.0-6.0.Fig. 60 ... nigrilamellatus (Macquart)

– Fore tibia without long apicoventral seta; frons silvery-white; fore knee yellow-red; cercus higher than long; 4.0 ... argentifrons Oldenberg

25. Proboscis elongated, equal approximately to 2/3 height of head; wing brown; cercus triangular; 3.0-3.5.Fig. 56 ... nigripennis (Fallén)

– Proboscis short ... 26

26. Mid basitarsus with a number of ventral setae; scutellum haired dorsally; 5.0 ... sahlbergi (Zetterstedt)

– Mid basitarsus without ventral setae; scutellum bare dorsally; 5^th segment of midtarsus slightly dilated; 5.0.Fig. 59 ... nigriplantis (Fallén)

27. Antennal stylus long pubescent, with hairs approximately 1.5 times longer than basal diameter of stylus; notopleuron having strongly pronounced purple spot ... 28

– Antennal stylus bare, rarely pubescent; notopleuron usually without purple spot ... 29

28. Antenna black; wing grey, with dark spot in apical part, transparent at apex behind M₁₊₂ ... nobilitatus (Linnaeus)

– Antenna partly yellow; wing evenly grey ... infuscatus (Stannius)

29. Metapleuron with group of hairs before posterior spiracle; posterior part of mesonotum and scutellum dorsally with hairs; R₄₊₅ and M₁₊₂ parallel ... 30

– Metapleuron and posterior part of mesonotum usually bare; scutellum usually without dorsal hairs; R₄₊₅ and M₁₊₂ usually convergent ... 38

30. Femora mainly dark, at most yellow on extreme apex ... 31

– Femora mainly yellow, at most infuscated on posterodorsal side ... 32

31. Clypeus bare; midtibia with several anteroventral setae; face wide, approximately twice wider than postpedicel; hind tibia mostly entirely yellow; larger species, total wing length more than 3.5 ... cupreus (Fallén)

– Clypeus pubescent; midtibia with only one anteroventral seta; face narrow, hardly wider than postpedicel; hind tibia distinctly infuscated on apex; smaller species, total wing length less than 3.5 ... angustifrons (Staeger)

32. Costa with a distinct, even if only slight, thickening between humeral crossvein and tip of subcosta, with thickest part at least as thick as next part of costa ... 33

– Costa without above thickening, this section distinctly and uniformly thinner than next section ... 34

33. Epistome with long pale pubescence; clypeus with short rather dark pubescence; postpedicel mostly slightly acute; fore coxa mainly dark, mostly yellow in apical 1/2 to 1/3, rarely slightly infuscated dorsally; hind basitarsus yellow at least in proximal half; hind tibia at most slightly infuscated in apical fifth; parameres pale brown with white tip ... celer (Meigen)

– Epistome with long dark pubescence; clypeus with short dark pubescence; postpedicel mostly obtuse; fore coxa mainly dark, mostly yellow on extreme apex; fore femora yellow, distinctly infuscated posterodorsally along whole length; hind basitarsus mostly entirely dark (when yellow, still darker than proximal part of tibia); hind tibia mostly slightly to distinctly infuscated in apical fifth; parameres black with white tip ... brevicornis (Staeger)

34. Clypeus with conspicuous pubescence ... 35

– Clypeus entirely bare ... 36

35. Fore and hind femora distinctly infuscated at least postero-dorsally; wings clear; proximal part of CuA₁ less than twice longer than apical part; proximal part of M₁₊₂ somewhat shorter than apical part; smaller species, total wing length about 3.0 ... aerosus (Fallén)

– All femora entirely pale yellow; wings clearly dark; proximal part of CuA₁ more than twice longer than apical part; proximal part of M₁₊₂ slightly longer than apical part; larger species, total wing length on average more than 4.0 ... metallicus (Stannius)

36. Mid tibia with 2 anteroventral setae; hind tibia entirely dark ... chalybeus (Wiedemann)

– Mid tibia with 1 anteroventral seta; hind tibia mostly yellow ... 37

37. Hind tibia distinctly infuscated in apical 1/4 to 1/3; fore and middle tarsi distinctly infuscated from apex of basitarsus onwards; hind basitarsus darker than proximal half of hind tibia; fore coxa mostly dark ... assimilis (Staeger)

– Hind tibia and basitarsus entirely yellow; fore and middle tarsi only feebly infuscated; fore coxa largely yellow, in particular on lateral side ... blankaartensis Pollet

38. Femora yellow ... 39

– Femora black ... 47

39. Lower postocular setae black ... 40

– Lower postocular setae light (white or yellow) ... 46

40. Antenna partly yellow ... 41

– Antenna entirely black ... 43

41. Lower calypter with black cilia ... chrysosygos (Wiedemann)

– Lower calypter with light (white or yellow) cilia ... 42

42. Postpedicel not longer than high, slightly brownish above and distally; hind tibia in distal half with comb of small posterodorsal setae ... rothi (Zetterstedt)

– Postpedicel slightly longer than high, distinctly darkened (brown or black) above and distally; comb of small posterodorsal setae on hind tibia weakly pronounced ... fulvicaudis (Walker)

43. Fore tibia without median posteroventral seta ... 44

– Fore tibia bearing 1 or more distinct, even though rather small, posteroventral seta ... 45

44. Scutellum haired ... nanus (Macquart)

– Scutellum bare ... females of the genus Sybistroma

45. Lower calypter with mostly light cilia ... gracilis (Stannius)

– Lower calypter with black cilia ... germanus Wiedemann

46. Proboscis and palpus yellow ... chetifer (Walker)

– Proboscis and palpus dark ... nanus (Macquart)

47. Lower postocular setae black ... nigrilamellatus (Macquart)

– Lower postocular setae light (white or yellow) ... 48

48. Proboscis elongated, at least half as long as head height ... nigripennis (Fallén)

– Proboscis short ... 49

49. Femora entirely black; hind tibia black at base and at apex; fore tibia with 8-10 setae ... sahlbergi (Zetterstedt)

– Apices of femora yellow; hind tibia black at apex only; fore tibia with 5-6 setae ... nigriplantis (Fallén)