Chaetocnema (Chaetocnema) tonkinensis Chen, 1934

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 : 109-110

42. Chaetocnema (Chaetocnema) tonkinensis Chen, 1934

( Fig. 63 )

Chaetocnema tonkinensis Chen, 1934: 246 , 250. TL: Vietnam, Tonkin. TD: MNHN

Distribution: China: Fujian, Jiangxi ( Gressitt & Kimoto, 1963), Jiangsu ( Yu et al., 1996), Hainan ( Gressitt & Kimoto, 1963), ( Chen, 1939); Vietnam ( Chen, 1934, Warchalowski, 1973); Thailand ( Kimoto, 2000).

Host plants: Poaceae .

Description: Body length: 1.70–1.80 mm. Body width: 1.00– 1.05 mm. Ratio of length of antenna to length of body: 0.65–0.68. Ratio of elytron length (along suture) to width (maximum): 2.25–2.30. Ratio of pronotum width (at base) to length: 1.70–1.72. Ratio of length of elytron to length of pronotum (along middle): 2.48–2.52. Ratio of width of elytra at base (in middle of humeral calli) to width of pronotum at base: 1.05–1.10.

Dorsum black, with hardly visible bronzy tinge on pronotum and head. Head finely reticulated. Antennae completely yellow brown, with distal 4 antennomeres darker. Tarsi and tibiae yellow brown. Pro- and mesofemora light brown. Metafemur black brown.

Head hypognathous. Frontal ridge narrow, convex. Frontolateral sulcus present. Suprafrontal sulcus poorly developed. Orbital, supraantennal sulci deep. Ratio of width of frontal ridge (excluding margin) to width of antennal socket (excluding margin): 1.15–1.20. Number of punctures on vertex: 3–5 on each side near eye. Number of punctures on orbit: 1–2 on each side. Number of punctures on frons (triangular area surrounded by frontolateral sulcus and clypeus): 0. Number of setae on clypeus: approximately 7. 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 present, rather prominent. Pronotal base convex, expanded at middle. Lateral margins of pronotum almost straight, converging forward. Anterolateral prothoracic callosity truncate, oblique and prominent. Posterolateral prothoracic callosity poorly developed. Pronotal punctures longitudinal, weak.

Elytra with slightly convex sides. Elytral punctures larger than those of pronotum, arranged in single rows, including peri-scutellar row. Elytral interspaces between puncture rows slightly costate at sides. Number of rows of minute punctures on each interspace: 1–2. Humeral callus well developed.

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

Apex of aedeagus in ventral view narrowing gradually. Ventral longitudinal groove absent. Apical denticle present in ventral view. Minute transverse wrinkles on ventral side absent. Aedeagus in lateral view unevenly curved, sinusoidal. Maximum curvature in lateral view situated at base.

Material: 1♂ ( USNM), China, Fujian, You-xi city env. WP-437/438, N 26° 17'806" E 118° 15'448", 30.V.2014, leg. A. Konstantinov.

Remarks: We could not locate the type specimen, species concept is based on original description provided by Chen (1934).

This species resembles C. hainanensis and C. longipunctata . It can be separated from C. longipunctata by the sparser punctures on pronotum and narrower body. It closely resembles C. hainanensis in the external characters, but obviously the shape of aedeagus is different.

We removed Chaetocnema tonkinensis taiwanensis Chûjô, 1965: 99 from synonymy with C. tonkinenis , as the former has been elevated to species. Chaetocnema tonkinensis has longer pronotum, darker body color, broader body and larger puntures along the base of pronotum.

Figures

FIGURE 63. Chaetocnema tonkinensis. 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.