Key to species (♂)

1. Vein Rs with basisetula (Fig. 30D)....................................................................... 17

Vein Rs without basisetula.............................................................................. 2

2. Posterior face of mid femur with sense-organ (Figs. 24D, 27D)................................................. 3

Posterior face of mid femur without sense-organ............................................................. 7

3. Sense-organ of mid femur including a rounded pit (or groove) and a apical process................................. 4

Sense-organ of mid femur only with a groove, but without a apical process........................................ 6

4. Sense-organ composed of a long groove and a long apical process (Fig. 24D)...................... C. formosensis Brues

Sense-organ with a rounded pit and a short apical process..................................................... 5

5. Sensory pit large, its diameter more than 1/2 width of mid femur (Fig. 26D); the aspect ratio of first flagellomere is 3:1.......................................................................................... C. tibialis Schmitz

Sensory pit small, its diameter less than 1/2 width of mid femur (Fig. 25D); the aspect ratio of first flagellomere equaled to or less than 2:1.......................................................................... C. simili s (Haliday)

6. The naked area at the base of posterior face of mid femur extends to half length of mid femur; the sensory groove is short and broad (Fig. 27D); basidorsal process of right surstylus long and finger-like (Fig. 27C).................. C. kempi Brunetti

The naked area at the base of posterior face of mid femur extends to one third of mid femur; the sensory groove is long and narrow (Fig. 28B), basidorsal process of right surstylus short, rectangular (Figs. 28D, F).............. C. rectangularis Liu

7. The base part of left surstylus is equaled to or broader than the apical part........................................ 8

The base part of left surstylus is significantly contracted and narrower than the apical part........................... 11

8. Left surstylus with a long, band-shaped basiprocess; posterior edge of left and right surstyli with 7–8 teeth respectively.... 9

Left surstylus without a long band-shaped basiprocess; posterior edge of left and right Surstyli only with1–4 teeth respectively......................................................................................... 10

9. Both anterior and posterior edges of surstylus are similar length, so the surstylus looks square (Figs. 4B–E).... C. ulrichi Liu

Anterior edge of surstylus longer than posterior edge, so the surstylus looks rhombic (Figs.3B–E) C. gracilis Michailovskaya

10. Apex of surstyli pointed (Figs. 1D–G); fine veins whitish gray(Fig. 29A)........................... C. dauci (Meigen)

Apex of surstyli blunt (Figs. 2B–E); wing with light-brown fine veins (Fig. 29C).................. C. obtusifinis sp. nov.

11. Both surstyli with concave, petal-like apical edge (Figs. 5B–E).................................. C. petalina sp. nov.

Surstyli without this features........................................................................... 12

12. Right surstylus long, slender, base part broader than the apex; left surstylus short.................................. 13

Right surstylus various shapes, base part narrower than the apex............................................... 15

13. Right surstylus parallel-sided, and the apex beak-shaped, with 3 long, thick, curved inner teeth (Figs. 9A–C, E).................................................................................................. C. spinifer a Liu

Right surstylus thin and lanceolate, and the apex not beak-shaped.............................................. 14

14. The apex of right surstylus suddenly becomes thinner, without inner teeth (Fig. 10D).................. C. longilobusa Liu

The apex of right surstylus gradually tapered, with 3 inner teeth (Fig. 10A).................. C. pacifica Michailovskaya

15. Fore femur with a brownish spot (Fig. 6A); left surstylus short, extending downwards, pointed apically, with a basidorsal and a adjacent small processes (Figs. 6D, F)............................................... C. maculifemoris sp. nov.

Fore femur without a brownish spot...................................................................... 16

16. Right surstylus is split into a rectangular upper branch and a crescent lower branch (Figs. 7C, E); left surstylus large and oval (Figs. 7B, D)........................................................................... C. forcipis sp. nov.

Right surstylus trapezoid (Figs. 8C, E); left surstylus enlarged apically, anchor-shaped (Figs. 8B, D)...................................................................................................... C. ancoraria sp. nov.

17. Left and right surstyli similar in shape, triangular or long banded.............................................. 18

Left and right surstyli very different...................................................................... 22

18. Both surstyli are long banded........................................................................... 19

Both left and right surstyli are nearly triangular............................................................ 20

19. Right surstylus with basidorsal process (Figs. 11C, E); left surstylus straight (Figs. 11B, D)............ C. angusta sp. nov.

Right surstylus lacking basidorsal process (Figs. 12C, E); left surstylus S-form curved (Figs. 12B, D)... C. tortuosa sp. nov.

20. Dorsal edge of left surstylus shorter than ventral edge; left and right surstyli symmetrical inversely (Figs. 14B–E).............................................................................................. C. convallis sp. nov.

Dorsal edge of left surstylus equaled to ventral edge......................................................... 21

21. Left surstylus with a short dorso-apical process, on which there are about 10 inner teeth (Figs. 15B, G); the dorso-apical corner of right surstylus pointed, with about 8 inner teeth (Figs. 15C, H).............................. C. chayuensis sp. nov.

Left surstylus without dorso-apical process and with 4–6 inner teeth (Figs. 15E, I); right surstylus with 6–8 inner teeth (Figs. 15F, J)............................................................................ C. triangularis sp. nov.

22. Right surstylus with a basidorsal process (Figs. 23F, H)...................................................... 28

Right surstylus without a basidorsal process............................................................... 23

23. Right surstylus oval or near square; inner teeth spread on the inner surface....................................... 24

Right surstylus trapezoidal or palm; inner teeth are mostly distributed on the edge................................. 25

24. Left surstylus oval, without a basidorsal process; with 16 inner teeth (Figs. 13B, E)............... C. dentisparsa sp. nov.

Left surstylus kidney-shaped, with a basidorsal process and a depression at the Apex; scattered with 1–5 inner teeth (Fig. 19B)..................................................................... C. quadrata Mostovski et Disney

25. Left surstylus axe-shaped (Figs. 17A, D)................................................. C. securiclata sp. nov.

Left surstylus without this feature....................................................................... 26

26. Right surstylus large, palmar-shaped, and lacking inner teeth (Figs. 18B, E)........................ C. palmata sp. nov.

Right surstylus small, with teeth........................................................................ 27

27. The apical edge of right surstylus wavy, with short setulae on surface (Figs. 16A, C, E)............ C. margiflucta sp. nov.

The apical edge of right surstylus slightly concaved; with long setulae on surface (Figs. 19F, H)......... C. longicilia Liu

28. Basidorsal process of right surstylus membranous.......................................................... 29

Basidorsal process of right surstylus sclerotized............................................................ 30

29. Left surstylus with a broad edge on basidorsal part (Figs. 20G, I); right surstylus with 2 small blunt basiprocess (Figs. 20H, J).................................................................................. C. marginata sp. nov.

Left surstylus only with a small basiprocess (Figs. 20B, D); right surstylus with 2 pointed basiprocess (Figs. 20C, E)............................................................................................. C. reniformis Liu

30. Frons without lower fronto-orbital setae; basidorsal process of left surstylus with inner teeth (Figs. 21B, D)................................................................................................ C. denticulata sp. nov.

Frons with lower fronto-orbital setae; basidorsal process of left surstylus without inner teeth......................... 31

31. The base of left surstylus not contracted (Figs. 21F, I, K); the inner teeth of the left and right surstyli thin and not sclerotized (same color with other setulae) (Fig. 21H)............................................. C. microspinulosa sp. nov.

The base of left surstylus contracted; the inner teeth of the left and right surstyli thick and sclerotized (darker than other setulae)............................................................................................ 32

32. Terminalia Large (Fig. 22A), length 0.40–0.44 mm; right surstylus with 14–18 inner teeth arranged in two rows (Figs. 22C, H)............................................................................. C. grandicaudata sp. nov. Terminalia small, length less than 0.35 mm; right surstylus with less than 10 inner teeth............................ 33

33. Posterior edge of right surstylus with 7 inner teeth, the undermost one is pointed (Figs. 22D, F, J); terminalia 0.31–0.33 mm ................................................................................. C. schnittmanni Schmitz

Posterior edge of right surstylus with 8–9 inner teeth, which all of them similar................................... 34

34. Basidorsal process of right surstylus short, inner teeth robust and blunt (Figs. 23A, C); terminalia 0.31–0.33 mm ........................................................................................... C. obtusidentis sp. nov.

Basidorsal process of right surstylus long, inner teeth slender and pointed (Figs. 23D, F, H); terminalia 0.31–0.33 mm ...................................................................................... C. digitalis Liu et Zhang