Key to species (males) of Amblypsilopus in the Himalayan region

1 Thorax with 4 strong dc and 3 strong acr; hind tarsomeres IV–V strongly flattened [China, Nepal]...................................................................................................... A. imitans (Becker, 1922)

- Thorax with 2 strong posterior dc and 3 hair-like anterior dc; other features various................................. 2

2 Hind tarsomeres IV–V distinctly widened; cercus filiform, with 2 long, strong apical bristles [India].................................................................................................... A. interditus (Becker, 1922)

- Hind tarsomeres normal or only tarsomeres V slightly widened; cercus various..................................... 3

3 Legs mainly black, with fore tibia and basal half of hind tibia dark yellow; cercus hairy, filiform, 2.0 times as long as epandrium [India]...................................................................... A. infans (Becker, 1922)

- Legs mainly yellow or wholly black; cercus various.......................................................... 4

4 Body length only 2.0 mm; thorax with 2 acr; cercus distinctly wide at base, with strong marginal dorsal bristles at basal half but no distinct apical bristle (Becker 1922, fig. 179) [India]................................ A. turbidus (Becker, 1922)

- Body length usually at least 3.0 mm; thorax usually with at least 3 acr............................................ 5

5 Cercus irregular, basal half 2.0 times as wide as apical half, only with bristles dorsally on basal half and apically (Becker 1922, fig. 180) [India, Nepal]........................................................... A. pediformis (Becker, 1922)

- Cercus triangular, band-like, lobate, filiform or digitiform...................................................... 6

6 Cercus nearly triangular, with long, strong dense bristles apically and ventrally, 1/3 to 2/3 as long as cercus (Becker 1922, fig. 181) [India]................................................................... A. penicillatus (Becker, 1922)

- Cercus variable in shape with only short hair-like marginal bristles.............................................. 7

7 Male without distinct bristle on fore tibia, with black bristle(s) on posterior vertex; size of hypandrium normal, surstylus without any cylindrical projection; other features various.........................................10 ( A. abruptus group)

- Male with distinct bristle(s) on fore tibia; other features various................................................. 8

8 Surstylus specialized, with 5 digitiform apical protuberances (Fig. 15) [China]................ A. quinquepetalus sp. nov.

- Surstylus without 5 digitiform protuberances................................................................ 9

9 Hypandrium reduced in size, bifurcated in ventral view, sharp apically (Yang et al. 2011, fig. 79) [China]............................................................................... A. liui Zhu & Yang, 2011 ( A. neoplatypus group)

- Hypandrium normal, not bifurcated [India]............................................. A. tenuipes (Becker, 1922)

10 Cercus distinctly longer than epandrium, band-like or filiform................................................. 11

- Cercus shorter than or almost as long as epandrium, shape various.............................................. 14

11 CuAx ratio 1.2; cercus pale except black apical ring, ribbon banding, with 4 long thin black marginal bristles at apical quarter ventrally, with 4 thick black apical bristles with truncate apex (Fig. 13) [China].................. A. marginatus sp. nov. - CuAx ratio at least 1.5; cercus with evenly color............................................................ 12

12 Cercus bifurcated basally; ventral branch wide but extremely short; dorsal branch rod-like, 1.2 times as long as epandrium, slightly expanded apically, with 3 apical digitations, each with 1 long strong apical bristle as long as cercus (Fig. 11) [China]........................................................................................ A. liangi sp. nov.

- Cercus filiform, not bifurcated, narrow at tip............................................................... 13

13 Cercus 2.0 times as long as epandrium, with thick ventral hairs (Yang et al. 2011, fig. 71); CuAx ratio 2.0 [China].................................................................................. A. subabruptus Bickel & Wei, 1996

- Cercus 4.0 times as long as epandrium, with a distinct ventral bristle at base (Yang et al. 2011, fig. 49); CuAx ratio 2.5 [China, India].......................................................................... A. abruptus (Walker, 1859)

14 Fore coxa wholly black................................................................................ 15

- Fore coxa wholly yellow or mainly yellow................................................................. 16

15 CuAx ratio 2.4; femora wholly black; cercus 1.5 times as long as epandrium (Yang et al. 2011, fig. 66) [Pakistan, India, Nepal, China]........................................................................ A. pusillus (Macquart, 1842)

- CuAx ratio 1.7; only basal third of fore femur, basal half of mid femur and dorsum of hind femur black; cercus 0.6 times as long as epandrium (Fig. 14) [China]..................................................... A. medogensis sp. nov.

16 Cercus nearly as long as epandrium or slightly longer than epandrium........................................... 17

- Cercus distinctly shorter than epandrium.................................................................. 22

17 Mid and hind coxae yellow (Fig. 1) [China]............................................... A. acuminatus sp. nov.

- Mid and hind coxae black.............................................................................. 18

18 Surstylus without obvious bristle; cercus wide, triangular (Yang et al. 2011, fig. 73) [China]........................................................................................................... A. xizangensis Yang, 1998

- Surstylus with 1–2 long bristles; cercus filiform............................................................ 19

19 Hypandrium with a long lateral arm (Yang et al. 2011, fig. 56) [China]......................... A. didymus Yang, 1997

- Hypandrium without branch or process................................................................... 20

20 Arista-like stylus 1.5 times as long as width of head; hypandrium with sinuous ventral margin in lateral view (Fig. 12) [China]...................................................................................... A. liratus sp. nov.

- Arista-like stylus nearly as long as or shorter than head width; hypandrium simple................................. 21

21 Epandrial lobe weak with 1 weak apical bristle; cercus with 1 strong spinous dorsal bristle at middle and 1 relatively long ventral bristle at apical quarter (Yang et al. 2011, fig. 105) [China]............................ A. insensibile (Yang, 1995)

- Epandrial lobe strong with 2 long strong apical bristles; cercus with strong apical bristles (Yang et al. 2011, fig. 59) [China]............................................................................ A. hubeiensis Yang & Yang, 1997

22 Fore tibia with pv at apical 1/5.......................................................................... 23

- Fore tibia without any pv [China]..................................................... A. baoshanus Yang, 1998

23 Mid tibia without distinct apical bristle; cercus only with marginal bristles dorsally (Yang et al. 2011, fig. 50) [China]........................................................................................ A. ampliatus Yang, 1995

- Mid tibia with 2 apical bristles; cercus with long, strong marginal bristles dorsally and ventrally (Yang et al. 2011, fig. 60) [China, India, Nepal]............................................................... A. humilis (Becker, 1922)