Key to the Asian species of subgenus Corynopus Lepeletier and Brullé

(Female of R. ataiyal and males of R. coarctatum koreense, R. xinjangense, R. babe and R. chettalicum sp. nov. are unknown)

1. Female............................................................................................. 2

- Male.............................................................................................. 11

2. Median lobe of clypeus rounded at apex................................................................... 3

- Median lobe of clypeus varying but not rounded apically...................................................... 6

3. Interantennal process much longer and pointed (Fig. 49 of Tsuneki 1974); tergum II narrow and reddish; clypeus slightly more narrowly rounded apically.............................................. R. coarctatum chosenense Tsuneki, 1974

- Interantennal process shorter and rounded; other characters varying............................................. 4

4. Clypeus median lobe elongated, narrow towards apex (Fig. 4 of Marshakov 1976); femur I all black, trochanter I black, trochanters II and III yellow; tergum I short, 1.5× longer than wide (Fig. 7 of Marshakov 1976)................................................................................................... R. kawabatai Marshakov, 1976

- Clypeus tridentate, central tooth rounded; other characters varying.............................................. 5

5. Fore and mid legs yellow except coxae brown, upper surface of femora and trochanters brown; hind leg reddish brown; tergum I elongate, 4.3× longer than wide (Figs 5–6 of Terayama et al. 2019)...................... R. babe Terayama et al., 2019

- Femur I black with yellow spot at apex; trochanters I and II yellow; hind tibia rusty red at apex, slightly widened; body slender; tergum I short, 3.0× longer than wide................................................ R. beaumonti Móczár, 1957

6. Median lobe of clypeus truncate or slightly emarginated apically................................................ 7

- Median lobe of clypeus slightly to conspicuously pointed at apex............................................... 9

7. Posterior lateral corner of propleuron with very small tooth; petiole almost as long as hind tibia (Fig. 2 of Li and Xue 1998).......................................................................... R. xinjiangense Li and Xue, 1998

- Posterior lateral corner of propleuron without small tooth; petiole varying........................................ 8

8. Scape and flagellum all black, pedicel dorsally so; fore femur all black, fore tibia with dorsal black spot; mid tibia with basal yellow ring; tergum I shorter than hind femur (Fig. 4b of Ratzlaff et al. 2016); pygidial plate without basomedian gibbosity................................................................................. R. gracile Wesmael, 1852

- Antennal scape yellow except medial black spot, pedicel all and flagellum ventrally yellow; fore femur with large apical yellow spot, fore tibia completely yellow; mid tibia yellow except black spot dorsally; tergum I longer than hind femur (Figs 1 & 2); pygidial plate with prominent basomedian gibbosity (Figs 14 & 15)............... R. chettalicum Saini and Dey, sp. nov.

9. Interantennal protuberance absent; abdominal petiole shorter than hind tibia (Fig. 9 of Li and Xue 1998); pygidial area narrow basally (Fig. 8 of Li and Xue 1998)............................................. R. gonopleurale Li and Xue, 1998

- Interantennal protuberance present; other characters varying.................................................. 10

10. Posterior lateral corner of propleuron with short, small obtuse angle; interantennal process simple, not dilated apically; pygidial plate narrower basally; hind tibia yellow basally, apical half bright reddish....... R. coarctatum coarctatum (Scopoli, 1763)

- Posterior lateral corner of propleuron without obtuse angle; interantennal process dilated and conical apically (Fig. 47 of Tsuneki 1974); pygidial plate slightly broader basally (Fig. 48 of Tsuneki 1974); hind tibia pale yellow basally, slightly reddish apically................................................................ R. coarctatum koreense Tsuneki, 1974

11. Occipital tooth indistinct, occipital carina gradually lowering towards apex, not reaching buccal cavity; no space between compound eyes and antennal sockets; antennae contiguous basally; interantennal protuberance tongue-shaped (Fig. 35 of Tsuneki 1982); antennomere IV and V slightly excavated beneath, VI markedly so (Fig. 36 of Tsuneki 1982)............................................................................................... R. ataiyal Tsuneki, 1982

- Occipital carina with or without tooth; other characters varying................................................ 12

12. Median lobe of clypeus truncate or sub-truncate apically..................................................... 13

- Median lobe of clypeus rounded or with small tooth apically.................................................. 15

13. Clypeus sub-truncate apically; tibia III with yellow basal ring or distinct reddish-brown ring; basitarsi I–III usual; antennomeres IV and V notched beneath......................................................... R. beaumonti Móczár, 1957

- Clypeus truncate apically; other characters varying.......................................................... 14

14. Tibia III basally light yellow, medially dark brown, apically rusty yellow; fore basitarsus wide; antennomeres II–VIII dark yellow, V–VIII notched beneath; interantennal tubercle notched........................ R. kawabatai Marshakov, 1976

- Tibia III black with yellow basal ring, without reddish apically; mid tarsal segments conspicuously expanded, basitarsus I and III slightly enlarged; flagellum dark brown to black; interantennal tubercle without notch........ R. gracile Wesmael, 1852

15. Anterior clypeal margin broad, with small tooth medially; antennomeres IV and V longer than other segments and notched beneath; fore basitarsus broad................................................. R. gonopleurale Li and Xue, 1998

- Anterior clypeal margin narrow and rounded; other characters varying.......................................... 16

16. Antennomere V notched beneath; antennomeres VI–VII, IX and XI white; occipital carina markedly produced into sharp toothshaped projection; mid basitarsus broadened to tooth-like projection............ R. coarctatum coarctatum (Scopoli, 1763)

- Antennomeres III and IV notched beneath, all segments black; occipital carina less produced into triangular process; mid basitarsus without tooth-like projection.................................... R. coarctatum chosenense Tsuneki, 1974