Chaetocnema (Chaetocnema) tristis Allard, 1889

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 : 113-115

44. Chaetocnema (Chaetocnema) tristis Allard, 1889

( Fig. 66 )

Chaetocnema tristis Allard, 1889: 307 . TL: Saigon, Vietnam. TD: MNHN.

Chaetocnema tristis (var.) fulvocostata Chen, 1933: 229. TL: Vietnam ( Tonkin). TD: MNHN.

Distribution: China (Guangxi, Yunnan, Tibet), Vietnam, Thailand, Indonesia.

Host plants: Unknown.

Description: Body Length: 3.50–4.00 mm, body width: 2.15–2.30 mm. Ratio of elytron length (along suture) to width (maximum): 2.30–2.40. Ratio of pronotum width (at base) to length: 1.30–1.50. Ratio of length of elytron to length of pronotum (along middle): 2.50–2.60. Ratio of width of elytra at base to width of pronotum at base (in middle of humeral calli): 1.15–1.20. Ratio of maximum width of elytra to maximum width of pronotum: 1.40–1.50.

Dorsum brown with obscure metallic luster, red yellow or yellow brown in some specimens. Antennomeres 1–6 completely yellow, 7–11 dark yellow to light brown. Tibiae and tarsi yellow. Pro- and mesofemora yellow. Metafemora dark brown.

Head hypognathous. Vertex unique: red yellow or red brown; highly raised, at higher plane than eye. Frontal ridge narrow, flat, slightly raised. Ratio of width of frontal ridge to width of antennal socket: 1.10–1.20. Frontolateral sulcus absent, represented by numerous large and closely placed punctures. Suprafrontal sulcus wide and deep, sinuated. Orbital sulcus deep and wide. No large punctures present on vertex, except one seta bearing supraorbital puncture adjacent to eye. A few minute punctures present on middle of vertex. Orbit extremely narrow. Number of punctures on frons (triangular area surrounded by frontolateral sulcus and clypeus): 0. Number of setae on clypeus: approximately 15. Number of setae on labrum: 6. Anterior margin of labrum slightly convex at middle.

Pronotum without longitudinal impressions near basal margin. Deep row of large punctures at base of pronotum absent. Pronotal base sinuated, expanded in middle. Lateral margins of pronotum almost straight or slightly convex with maximum width near base. Anterolateral prothoracic callosity truncate and long, oblique, protruding antero- laterally. Posterolateral prothoracic callosity poorly developed. Diameter of pronotal punctures 2–4 times smaller than distance between them.

Elytra with convex sides, surface obviously costate between puncture rows. All rows of elytral punctures regular and single. Interspaces between striae of punctures with 2–4 rows of minute punctures. Humeral callus well developed. Width of elytral base greater than width of pronotal base

First male protarsomere slightly larger than second. Excavation on metatibia very deep. Large lateral denticle on metatibia obtuse. Metatibial serration proximal to large lateral denticle absent.

Apex of aedeagus in ventral view gradually narrowing. Ventral longitudinal groove poorly developed. Apical denticle in ventral view small and acute. Minute transverse wrinkles on ventral side absent. Aedeagus in lateral view unevenly curved, maximum curvature situated basally.

Spermathecal receptacle flask-shaped. Basal part of spermathecal duct straight. Spermathecal pump much shorter than receptacle, with flat apex. Receptacle basally much wider than apically. Apex of vaginal palpus round- ed, with lateral margin slightly convex. Middle part of vaginal palpus obviously narrowed. Anterior end of anterior sclerotization rounded.

Type: Chaetocnema tristis (var.) fulvocostata Chen: ♂ (Holotype) ( MNHN): 1) Museum Paris, Laos, Ou Cam- bodge, Bonnotte, 1911. 2) Type. 3) C. tristis fulvocostata, S. H. Chen det.

Material: 1♀, China: Guangxi, Yangsuo , 24.VIII.1937 ; 1♀, China: Yunnan, Xishuanbanna, Xiaomenyang , alt. 850m, 17.VII.1957, leg. Shuyong Wang, Chaetocnema tristis det. Peiyu Yu ; 1♀, China: Motuo, Gelin , Xizang, 19.V.1983. leg. Zai Lin, Chaetocnema sp., ( IZCAS) ; 1♀, Vietnam: Tonkin, Chaetocnema tristis det. S. H. Chen ; 1 ( USNM), Vietnam: Buon Loi , 40km W Ankne, alt. 600m, IV.1981, leg. Medvedev et al., Chaetocnema tristis det. Med. ; 1 ( MNHN), Vietnam, Reg. De Luc–Nam (Tonkin), L. Blaise, Museum Paris , Coll. L. Bedel, 1922, Chaetocnema tristis All., S. H. Chen det .; 1 ( BMNH), NW Thailand, 19°19'N, 97°59'E, Mae Hong Son, 1991, San Huai Po , 1600–2000m, 17.–23.5., L. Dembicky leg., BMNH(E), 2002–150, Chaetocnema spp. det. K. Nadein 2007, Chaetocnema tristis Allard, 1889 , Det. Yongying Ruan, 2016.

Remarks: Chaetocnema tristis is very close to C. simplicifrons in the shape of spermatheca and pygidium. However, C. tristis (length 3.5–4.0 mm) is distinctly larger than C. simplicifrons (length 1.65–1.8 mm).

Figures

FIGURE 66. Chaetocnema tristis. A Male habitus. B Pronotum and peri-scutellar area. C Head, frontal view. D Aedeagus, ventral view. E Aedeagus, lateral view. F Apex of aedeagus, ventral view. G Vaginal palpi. H Spermatheca. I Pygidium (tergite 7) of female. J Tignum.