Key to males of NW European species of Drapetis

1 Radial-medial crossvein (r–m) situated at or before the middle of the basal medial cell (bm) (Fig. 2A) … ( D. assimilis -group)................................................................................................... 2

– Radial-medial crossvein (r–m) situated beyond the middle of the basal medial cell (bm) (Figs 2B, C) … ( D exilis -group)... 7

2 Proepisternum shiny black. Pedicel beneath with 1–2 elongate setae. Knob of halter dusky brown..................... 3

– Proepisternum grey pruinose. Pedicel with short setae only. Knob of halter pale yellow............................. 6

3 Proepisternum bare except for two setae at base. Hind femur with a row of long pale posteroventral setae in basal two-thirds (Fig. 3A)........................................................................................... 4

– Proepisternum also with a pale up-turned seta arising from the middle. Hind femur with pale posteroventral setae confined to basal third or absent.................................................................................… 5

4 Face and clypeus shiny black. Legs extensively blackish brown, paler brown on foreleg. Male terminalia (Collin 1961, fig. 12a)................................................................................ … assimilis (Fallén)

– Face and clypeus grey pruinose. Legs extensively yellowish to yellow brown, only more or less darkened dorsally on femora. Male terminalia (Kovalev 1972, figs 1–3)...................................................… ingrica Kovalev

5 Hind femur with posteroventral row of pale setae in basal third. Male terminalia (Collin 1961, fig. 13a)... … arcuata Loew

– Hind femur without posteroventral setae. Male terminalia (Collin 1961, fig. 12b).................... … simulans Collin

6 Scape and pedicel black. Fore tarsi yellowish with blackish apical tarsomere...................... … convergens Collin

– Scape and pedicel orange yellow. All tarsi of uniform brownish colour. Male terminalia (Grootaert et al. 2010, figs 5–8).......................................................................................... flavipes Macquart

7 Mid tibia simple....................................................................................… 8

– Mid tibia ventrally expanded and compressed, with numerous denticles on its ventral edge (Figs 3C, 4A, C). Male terminalia (Figs 1 A–D).......................................................................... abrollensis sp. nov.

8 Mid femur in front with transverse cuticular ribs (Figs 5C, E, 6 A–D) or fine furrows (Figs 5B, D) and with usual ground setulae very short or absent.................................................................................… 9

– Mid femur simple, in front with practically smooth cuticle and a uniform cover of setulae (Fig. 5A).................. 13

9 Mid femur in front with a variable pattern of transverse cuticular ribs (Figs 5C, E, 6 A–D).......................... 10

– Mid femur in front with numerous linear transverse furrows (Figs 5B, D). Male terminalia (Collin 1961, fig. 14a)................................................................................................ … exilis Meigen

10 Knob of halter dark. Scape and pedicel brownish black................................................... … 11

– Knob of halter white. Scape reddish brown, pedicel ochre yellow. Male terminalia (Grootaert 2016, figs 6–8)............................................................................................ … bruscellensis Grootaert

11 Fore femur anteroventrally without a recurved apical seta. Mid femur with field of transverse ribs in anterior position (Figs 5C, 6A).............................................................................................… 12

– Fore femur anteroventrally with a recurved apical seta (Fig. 3B). Mid femur with anterodorsal field of ca. 18 transverse ribs and valleys devoid of setulae (Figs 6B, D). Male terminalia (Grootaert 2016, figs. 12–14)................... … pusilla Loew

12 Setulae beneath antennal pedicel reaching length of pedicel. Mid femur with anterior field of more than 20 transverse ribs crossed by a single row of short setulae (Figs 6A, C). Male terminalia (Grootaert 2016, figs 9–11)......... … parilis Collin

– Setulae beneath antennal pedicel shorter than length of pedicel. Mid femur with anterior field of less than 15 short transverse ribs covered in short setulae (Figs 5C, E). Male terminalia (Collin 1961, fig. 14b).................... … infitialis Collin

13 Longitudinal wing veins of regular thickness, membrane almost clear; vein R 4+5 fully developed until wing margin (Fig. 2A) …................................................................................................ 14

– Longitudinal wing veins thickened, membrane conspicuously clouded; vein R 4+5 pale and faded shortly before wing margin (Fig. 2C). Male terminalia (Kovalev 1972, figs 8, 9)............................................ incompleta Collin

14 Hind femur thinner than fore femur. Male terminalia with two strong, spine-like setae on left surstylus 1 and two similar setae on right surstylus (Kovalev 1972, figs 15, 16, 24).........................................… stackelbergi Kovalev

– Hind femur as thick as fore femur. Male terminalia without prominent, spine-like setae (Kovalev 1972, figs 17–19, 24)........................................................................................ … completa Kovalev