Chaetocnema, Ruan & Yang & Konstantinov & Prathapan & Zhang, 2019

Ruan, Yongying, Yang, Xingke, Konstantinov, Alexander S., Prathapan, Kaniyarikkal D. & Zhang, Mengna, 2019, Revision of the Oriental Chaetocnema species (Coleoptera, Chrysomelidae, Galerucinae, Alticini), Zootaxa 4699 (1), pp. 1-206 : 23-25

Key to species of subgenus Chaetocnema s. str.

1. Frontal ridge wide and flat, width of frontal ridge to width of antennal socket exceeds 2.20; vertex evenly covered with numerous (more than 30) extremely shallow and medium sized punctures, leaving a middle longitudinal area impunctate; lateral margin of pronotum nearly straight, converging forward...................................................... 2

- Frontal ridge narrow and convex, width of frontal ridge to width of antennal socket ratio less than 2.0; vertex only punctate on sides near eyes or with numerous extremely minute and ragged punctures scattered over entire vertex.................. 5

2. Interspaces between puncture rows of elytra densely punctate and transversely wrinkled................................................................................................ Chaetocnema nagpurensis Duvivier, 1892

- Interspaces between puncture rows of elytra not wrinkled..................................................... 3

3. Body broad. Elytra yellow, without metallic luster, with peri-scutellar area and suture brown (yellow pattern on elytra could be weaker in some specimens)............................................. Chaetocnema granulicollis Jacoby, 1896

- Elytra not yellow, with metallic luster..................................................................... 4

4. Dorsum unicolorous, bronzy, without green luster; pronotum wide, approximately twice wider than long.......................................................................................... Chaetocnema jinxiuensis sp. nov.

- Dorsum slightly bicolorous, pronotum and head bronzy green; elytra bronzy, with very slight green tinge; pronotum long, longer than regular Chaetocnema species, about 1.5 times wider than long................. Chaetocnema trapezoida sp. nov.

5. Sides of vertex strongly raised, higher than level of orbit and eye; from lateral view, lateral sides of vertex forming vertical walls............................................................................................... 6

- Vertex normal, not raised, situated on same level as orbit and eye.............................................. 10

6. Dorsum metallic blue, interspaces between puncture rows of elytra covered with conspicuous, dense and minute punctures................................................................... Chaetocnema yunnanica Heikertinger, 1951

- Body not metallic blue, interspaces between puncture rows of elytra sparsely and very minutely punctate............... 7

7. Body length greater than 3.40 mm .............................................. Chaetocnema tristis Allard, 1889

- Body length less than 2.50 mm .......................................................................... 8

8. Pronotum bumpy, with ragged and unevenly distributed punctures............... Chaetocnema simplicifrons ( Baly, 1876)

- Pronotum smooth, with normal punctures.................................................................. 9

9. Antero-lateral calli of pronotum strong and truncate; body color bronzy..... Chaetocnema puncticollis ( Motschulsky, 1858)

- Antero-lateral calli of pronotum weak and facing forward; body color blackish brown...................................................................................................... Chaetocnema furthi Medvedev, 1996

10. Numerous extremely minute and ragged punctures scattered over entire vertex, leaving some area impunctate; pronotum covered with minute punctures; head and pronotum smooth and shiny, without any fine reticulated pattern as in other species... .................................................................................................. 11

- Vertex only with sides near eyes covered with large punctures; pronotum covered with large punctures; head and pronotum regularly finely reticulated............................................................................. 15

11. Surface of frontal ridge covered with numerous extremely minute punctures; upper part of frontal ridge wider than lower part......................................................................... Chaetocnema sticta Maulik, 1926

- Surface of frontal ridge without numerous minute punctures; frontal ridge parallel-sided............................ 12

12. Surface of frontal ridge covered with transverse wrinkles; body with dark purplish metallic luster................................................................................................. Chaetocnema purerulea sp. nov.

- Surface of frontal ridge smooth; body without purple metallic luster............................................ 13

13. Body longer than 2.90 mm; antennae rather long, reaching well over humeral calli................................. 14

- Body shorter than 2.70 mm; antennae of normal length, reaching humeral calli of elytra. Chaetocnema duvivieri Jacoby, 1892

14. Body narrow and longitudinal, parallel-sided; tibiae and tarsi yellowish brown; antennae reaching middle of elytra............................................................................. Chaetocnema excavata Medvedev, 1997

- Body broad, ovate; tibiae and tarsi generally dark brown; antennae reach well over humeral calli, but not attaining middle of elytra.................................................................... Chaetocnema melonae Chen, 1934

15. A transverse row of enlarged and deepened punctures present along the base of pronotum; pronotal punctures either extremely minute or longitudinal................................................................................ 16

- Punctation near the base of pronotum normal, without a row of enlarged or deepened punctures...................... 28

16. Frontal ridge broad, width of frontal ridge to width of antennal socket ratio usually exceeds 1.40; pronotal punctures minute, conspicuously longitudinal............................................................................. 17

- Frontal ridge narrow, width of frontal ridge to width of antennal socket ratio less than 1.40; pronotal punctures extremely minute and shallow, round................................................................................ 22

17. Antennae and legs extremely robust and long, disproportionate to the size of body; hind tibiae with extremely deep excavation and strongly produced tooth................................................ Chaetocnema appendiculata sp. nov.

- Antennae and legs normal; hind tibia with normally developed excavation and tooth............................... 18

18. Body color brown, sometimes with very slight coppery luster................................................. 19

- Body color black, sometimes with very slight bronzy luster................................................... 20

19. In ventral view, aedeagus with sides of basal opening much expanded, prominently wider than the rest part of aedeagus........................................................................... Chaetocnema hongkongensis sp. nov.

- In ventral view, aedeagus with sides of basal opening only slightly expanded............. Chaetocnema yiei Kimoto, 1970

20. Surface of vertex with 8–12 punctures on each side near eye; labrum strongly and evenly concave at anterior margin, forming teeth at sides........................................................ Chaetocnema longipunctata Maulik, 1926

- Surface of vertex with less than 7 punctures on each side near eye; labrum straight or very slightly convex at anterior margin, not forming teeth at sides.............................................................................. 21

21. In ventral view, aedeagus asymmetrical, apical denticle of aedeagus bent towards right side; in lateral view, aedeagus very slightly bent ventrally; body much more broadened than allied species, elytron length (along suture) to width (maximum): 1.75–1.85................................................................... Chaetocnema nigrilata sp. nov.

- In ventral view, aedeagus symmetrical, apical denticle of aedeagus upright; in lateral view, aedeagus strongly bent ventrally at base, slightly bent dorsally at apical half...................................... Chaetocnema tonkinensis Chen, 1934

22. Body longer than 1.90 mm. Body robust, cylindrical and slightly longitudinal, not broad; frontal ridge wider than antennal socket............................................................................................. 23

- Body shorter than 1.90 mm. Body very broad, very much ovate; frontal ridge not wider than antennal socket............ 24

23. Body entirely black, elytra strongly costate...................................... Chaetocnema babai Kimoto, 1991

- Body brown, elytra only very slightly costate at sides........................... Chaetocnema taiwanensis Chûjô, 1965

24. Pronotal punctures longitudinal; body color entirely black, without any metallic luster.............................. 25

- Pronotal punctures circular; body color not entirely black.................................................... 26

25. Punctures below antennal socket (i.e., the area near clypeus) geminate or tripled; aedeagus gradually narrowed.............................................................................. Chaetocnema warchalowskii Döberl, 2009

- Punctures below antennal socket (i.e., the area near clypeus) single or slightly geminate; aedeagus abruptly narrowed.......................................................................... Chaetocnema nigrica Motschulsky, 1858

26. Pronotum covered with evenly spaced shallow and minute punctures; transverse row of enlarged punctures at pronotal base prominent at sides, weak at middle; basal margin of pronotum well depressed and ridged........................... 27

- Pronotum extremely glabrous and smooth, almost impunctate, only a few punctures scattered irregularly; transverse row of enlarged punctures only occur at sides of pronotal base; basal margin of pronotum flat, almost not depressed............................................................................... Chaetocnema fallaciosa Heikertinger, 1951

27. Dorsum yellowish brown to reddish brown, with very slight metallic luster on pronotum; antennae long, reaching beyond middle of elytra.................................................. Chaetocnema resplendens Warchalowski, 1973

- Dorsum black with bronzy luster; antennae not stretching beyond middle of elytra...... Chaetocnema yaosanica Chen, 1939

28. In lateral view, aedeagus with middle part straight, apical and basal part bent ventrally, apical denticle bent dorsally or straight............................................................................................ 29

- In lateral view, aedeagus curved at middle................................................................. 31

29. Body cylindrical and longitudinal, with lateral sides almost parallel............... Chaetocnema hainanensis Chen, 1933

- Body ovate, with lateral sides convex.................................................................... 30

30. Pronotum covered with extremely coarse punctures as large as those on elytra........... Chaetocnema sabahensis sp. nov.

- Pronotum covered with extremely minute and shallow, barely visible punctures......... Chaetocnema dapitanica sp. nov.

31. Frontal ridge wide, width of frontal ridge to width of antennal socket ratio exceeds 1.40............................ 32

- Frontal ridge narrow, width of frontal ridge to width of antennal socket ratio less than 1.40.......................... 36

32. Body minute, body length less than 1.80 mm (body length of North American specimens slightly greater. Only female specimens have been discovered in Oriental Region)................................. Chaetocnema confinis Crotch, 1873

- Body size medium to large, body length greater than 2.40 mm ................................................. 33

33. Body color metallic blue; elytra only slightly costate at sides................... Chaetocnema philippina Medvedev, 1996

- Body color brown; elytra strongly costate................................................................. 34

34. Body length exceeding 3.50 mm; body cylindrical and longitudinal; ventral-lateral sides of aedeagus without prominent oblique ridges.................................................................... Chaetocnema wallacei Baly, 1877

- Body length 2.90–3.20 mm; body ovate and broad;.two oblique ridges and numerous streaks occur on ventral-lateral sides of aedeagus........................................................................................... 35

35. Two oblique ridges present on ventral sides of aedeagus, conspicuously expanded, forming a narrow wing-like sclerotization...................................................................... Chaetocnema sumatrana Jacoby, 1896

- Two oblique ridges on aedeagus narrow, ridge-like, not expanded................. Chaetocnema montivaga Maulik, 1926

36. Antero-lateral calli of pronotum prominently facing forward, acute, very weak at sides; body strongly narrowing anteriorly, head rather narrow (much narrower than width of anterior margin of pronotum)................................... 37

- Antero-lateral calli of pronotum not acute and facing forward, usually rounded or truncate.......................... 39

37. Interspaces of elytral puncture rows prominently covered with transverse wrinkles; each side of head near eye covered with approximately 15 punctures; body narrowing both anteriorly and posteriorly... Chaetocnema fusiformis Chen & Wang, 1980

- Interspaces of elytral puncture rows covered with circular minute punctures; each side of head near eye covered with approximately 5-10 punctures................................................................................ 38

38. Body length: 1.70–1.85 mm; tibiae dark brown, with base near femora slightly yellowish brown.............................................................................................. Chaetocnema parafusiformis sp. nov.

- Body length: 1.40–1.70 mm; tibiae yellowish brown......................... Chaetocnema gracilis Motschulsky, 1858

39. Body length approximately 2.5 mm; body metallic blue, with pronotum slightly greenish Chaetocnema yonyonae Chen, 1934

- Body length less than 2.5 mm; body not metallic blue....................................................... 40

40. Dorsum with green to greenish blue metallic luster; each side near base of pronotum without indistinct longitudinal strip......................................................................... Chaetocnema laotica Medvedev, 2009

- Dorsum without greenish or bluish luster, regularly with bronzy to coppery luster; each side near base of pronotum with or without short longitudinal depression.................................................................... 41

41. Each side near base of pronotum without short longitudinal depression; body shape broad, very much resembles C. nigrica , however without transverse row of enlarged punctures along pronotal base; body entirely black, with very slight bronzy luster Chaetocnema subbasalis sp. nov.

- Each side near base of pronotum with very short and indistinct (sometimes nearly invisible) longitudinal impression; body narrow............................................................................................... 42

42. Appendages stronger and longer than in regular species; length of antenna to length of body ratio: about 0.70; pronotum long, almost parallel-sided; humeral calli extremely weak......................................................... 43

- Appendages as normal as regular species; length of antenna to length of body ratio smaller than 0.70.................. 44

43. Aedeagus somewhat narrowed at apex, with apical denticle weak and angulate........................................................................................ Chaetocnema kingpinensis Ruan, Konstantinov & Yang, 2014

- Aedeagus parallel-sided, apex as wide as middle and base, apical denticle entirely absent. Chaetocnema baoshanica sp. nov.

44. Body black, with or without metallic luster; antennae and legs deep brown to black................................ 45

- Body brown, with bronzy to coppery luster; antennae and legs brown to yellow................................... 46

45. Body color black, elytra without any metallic luster, pronotum with bronzy luster; appendages with brown color.................................................................. Chaetocnema salixis Ruan, Konstantinov & Yang, 2014

- Body black with very slight bronzy luster; appendages mostly dark brown............ Chaetocnema malaisei Bryant, 1939

46. In ventral view, aedeagus dilated or widened at apical part.................................................... 47

- In ventral view, aedeagus narrower at apical part than middle................................................. 49

47. In ventral view, aedeagus with perfect straight lateral sides, evenly expanding from base to apical part; apical part of aedeagus nearly triangulate, with tip broadly angulated.................... Chaetocnema cheni Ruan, Konstantinov & Yang, 2014

- In ventral view, aedeagus parallel-sided, not expanding from base to apical part, only dilated and rounded at apex........ 48

48. Aedeagus symmetrical, very slightly dilated at apex in ventral view............... Chaetocnema fortecostata Chen, 1939

- Aedeagus assymmetrical, distorted at base, strongly dilated at apex in ventral view..... Chaetocnema granulosa Baly, 1874

49. Ventral groove present at ventral side of aedeagus; aedeagus abruptly narrowed and constricted right before apical top; body color usually bronzy................................... Chaetocnema constricta Ruan, Konstantinov and Yang, 2014

- Ventral groove absent at ventral side of aedeagus........................................................... 50

50. In lateral view, aedeagus evenly curved, slightly sinuate at apex; body color usually bronzy............................................................................... Chaetocnema deqinensis Ruan, Konstantinov & Yang, 2014

- In lateral view, aedeagus straight at basal half, bent ventrally at apical half, slightly sinuate at apex; body color usually coppery................................................ Chaetocnema yulongensis Ruan, Konstantinov & Yang, 2014