Key to species of Macrosteles from China (males)

1 Aedeagus in lateral view with terminal appendages abruptly curved caudad or ventrad............................... 2

- Aedeagus in lateral view with terminal appendages more or less continuing with curvature of shaft, extending dorsad or cephalad............................................................................................. 8

2 Aedeagal shaft short, with terminal appendages short and divergent in caudal view (Plate 7, figs. 7–10) (frontalis species- group)................................................................................... M. harperatus

- Aedeagal shaft elongate, with terminal appendages parallel or crossing at base..................................... 3

3 Aedeagus with apical appendages short, less than half of shaft length; aedeagal shaft with pair of protuberances laterally sub- apically (Plate 8, figs. 3, 4) ( guttatus species-group).................................................. M. guttatus

- Aedeagus with apical appendages long, generally longer than half of shaft length; aedeagal shaft without protuberances later- ally subapically (Plates 12, 13) (variata species-group)........................................................ 4

4 Aedeagal shaft with pair of protuberances dorsally subapically (Plate 13, figs. 5, 6)......................... M. brochus

- Aedeagal shaft without protuberances dorsally subapically..................................................... 5

5 2nd tergal apodeme with posterior lobes extending well beyond posterior margin of tergite (Plate 13, fig. 25)..... M. striifrons

- 2nd tergal apodeme with posterior lobes not extending beyond posterior margin of tergite............................. 6

6 Aedeagal shaft with several teeth dorsally and baso-ventrally; 2nd sternal apodemes with posterior lobes twice as long as basal width (Plate 12, figs. 13, 14, 18)............................................................... M. albicostalis

- Aedeagal shaft smooth; 2nd sternal apodemes with posterior lobes less than twice as long as basal width................. 7

7 Aedeagus with apical appendages long, twisted, lying distad of shaft; 1st sternal apodemes with anterior lobes well developed (Plate 12, figs. 5, 6, 8)......................................................................... M. abludens

- Aedeagus with apical appendages comparatively short, lying near shaft; 1st sternal apodemes with anterior lobes reduced (Plate 13, figs. 13, 14, 16)....................................................................... M. parastriifrons

8 Vertex with 4 black or brown spots (Plate 9) ( quadripunctulatus species-group).................................... 9

- Vertex with 3 pairs of black or brown spots, sometimes spots merged irregularly................................... 11

9 Pygofer without caudo-ventral tubercle; aedeagal shaft with dorsal protuberance subapically (Plate 9, figs. 13, 14)............................................................................................... M. quadrimaculatus

- Pygofer with caudo-ventral tubercle; aedeagal shaft without protuberance subapically.............................. 10

10 Apical aedeagal appendages branched (Plate 9, figs. 22–24).................................... M. quadripunctulatus

- Apical aedeagal appendages unbranched (Plate 9, figs. 5, 6)........................................... M. brunneus

11 Aedeagal appendages apically convergent or crossing........................................................ 12

- Aedeagal appendages apically divergent or parallel.......................................................... 18

12 Appendages of aedeagal shaft distinctly sinuate, conjoined bases above gonopore angled cephalad, processes above this directed dorsad (Plates 5, 6) ( fieberi species group).......................................................... 13

- Appendages of aedeagal shaft evenly curved or straight in lateral aspect (Plates 10, 11) ( sordidipennis species-group)..... 15

13 Aedeagus without lateral flanges, with stout teeth laterally and ventrally on shaft, 2nd acrotegite usually horizontal (Plate 5, figs. 15–19)................................................................................. M. spinosus

- Aedeagus with lateral flanges, 2nd acrotegite usually V-shaped (Plate 5, fig. 8; Plate 6, fig. 6)........................ 14

14 2nd sternal apodeme with posterior lobes reduced, shorter than basal width (Plate 5, fig. 10).................... M. lividus

- 2nd sternal apodeme with posterior lobes longer than basal width (Plate 6, fig. 9)........................ M. viridigriseus

15 1st abdominal sternal apodemes with anterior lobes well-developed and long (Plate 10, figs. 8, 9)............... M. ehensis

- 1st abdominal sternal apodemes with anterior lobes short and narrow............................................ 16

16 2nd acrotergite with trunk and neck generally thin (Plate 11, fig. 5)...................................... M. heitiacus

- 2nd acrotergite with trunk and neck conspicuously thick and stout............................................... 17

17 2nd abdominal sternal apodemes with posterior lobes robust, length about 1.5 times basal width (Plate 10, fig. 20). M. gracilis

- 2nd abdominal sternal apodemes with posterior lobes elongated strikingly, length about 2.5 times basal width (Plate 11, fig. 17)....................................................................................... M. sordidipennis

18 Aedeagus with appendages short and slim, sickle-shaped in later aspect (Plate 4) ( falcatus species-group)................ 19

- Aedeagal appendages simple, moderately long and broad (Plates 1–3) ( alpinus species-group)........................ 20

19 Aedeagal shaft broad ventrally, with serrated flanges laterally (Plate 4, figs. 5, 6)............................. M. choui

- Aedeagal shaft slender ventrally, with symmetric teeth arising directly from shaft laterally (Plate 4, figs. 15, 16).. M. falcatus

20 Vertex unmarked; apical aedeagal appendages sinuate, with tips recurved posterad in lateral aspect (Plate 2, figs. 1, 3).................................................................................................. M. tibetensis

- Vertex with 4-6 dark spots; apical aedeagal appendages not sinuate in lateral aspect................................ 21

21 Aedeagal shaft distinctly swollen in lateral view (Plate 1, figs. 11, 12)................................... M. cristatus

- Aedeagal shaft evenly tapered in lateral view............................................................... 22

22 Aedeagal shaft smooth, with apical appendages strongly curved dorsally......................................... 23

- Aedeagal shaft not smooth, with apical appendages shallowly curved dorsally.................................... 24

23 2nd acrotergite with trunk widely V-shaped; 2nd tergal apodemes with posterior lobes apparently extending beyond posterior margin of tergite (Plate 2, fig. 13)................................................................... M. laevis

- 2nd acrotergite with trunk comparatively small and nearly horizontal; 2nd tergal apodemes with posterior lobes not extending beyond posterior margin of tergite (Plate 3, figs. 14–16)................................................ M. nabiae

24 Aedeagal shaft usually parallel-sided, with a row of teeth laterally; 2nd acrotergite with trunk horizontal (Plate 1, figs. 4, 5)............................................................................................... M. alpinus

- Aedeagal shaft strikingly extended laterally, with lateral flanges broadly developed mesally; 2nd acrotergite with trunk widely V-shaped (Plate 3, figs. 4–6).................................................................... M. lindbergi