Chaetocnema (Chaetocnema) taiwanensis Chûjô, 1965

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 : 107-109

41. Chaetocnema (Chaetocnema) taiwanensis Chûjô, 1965 (New Status, elevated to species)

( Fig. 62 )

Chaetocnema tonkinensis taiwanensis Chûjô, 1965: 99 ; TL: China (Musha, Taiwan). TD: KMNH. (New Status, elevated to species)

Distribution: China (Taiwan).

Host plants: Unknown.

Description: Body length: 1.95–2.10 mm. Body width: 1.10–1.13 mm. Ratio of elytron length (along suture) to width (maximum): 2.62–2.65. Ratio of pronotum width (at base) to length: 1.65–1.70. Ratio of length of elytron to length of pronotum (along middle): 3.10–3.20. Ratio of width of elytra at base (in middle of humeral calli) to width of pronotum at base: 1.06–1.08.

Dorsum dark brown. Dorsum and head smooth and shiny, not rugose. Antennomeres 1-6 completely yellow brown, 7-11 brown. Tarsi yellow brown. Tibiae, pro- and mesofemora light brown. Metafemur dark brown.

Head hypognathous. Frontal ridge narrow and convex. Frontolateral sulcus present, with numerous punctures and white setae. Suprafrontal sulcus shallow, concave at middle. Orbital, supraantennal sulci deep. Ratio of width of frontal ridge (excluding margin) to width of antennal socket (excluding margin): 1.20–1.25. Number of punctures on vertex: 2–4 on each side near eye. Number of punctures on orbit: 2–3 on each side. Number of setae on clypeus: approximately 20. Number of setae on labrum: 6. Anterior margin of labrum straight.

Pronotum without longitudinal impressions near basal margin. Deep transverse row of large punctures at base of pronotum poorly developed, present laterally, absent in middle. Pronotal base convex, slightly expanded in middle. Lateral margins of pronotum evenly convex, somewhat converging forward. Both anterolateral and posterolateral prothoracic callosities poorly developed. Pronotal punctures extremely minute and shallow. Diameter of pronotal punctures 3–5 times smaller than distance between them.

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

Excavation on metatibia shallow. Large lateral denticle on metatibia obtuse. Metatibial serration proximal to large lateral denticle absent or poorly developed.

Type: ♂ (Holotype) ( KMNH), 1) Musha Formosa 23.VI.1961; 2) Holotype; 3) Chaetocnema (Tlanoma) tonkinensis taiwanensis Chûjô, Det, M. Chûjô, 1962 ; 4) a blank yellow label.

Remarks: This species was originally published as a sub-species of Chaetocnema tonkinensis Chen , and was subsequently synonymized with the same species by Kimoto (1970: 208). However, based on the study of the Holotype, we conclude that it is quite distinct from Chaetocnema tonkinensis Chen and here we elevate it to species level. Chaetocnema tonkinensis has longer pronotum, darker and broader body and larger puntures along the base of pronotum compared to C. taiwanensis .

Chaetocnema taiwanensis also resembles C. yiei and C. babai . It can be easily distiguished from the latter two species by the narrower frontal ridge and the presence of a notch in the middle of suprafrontal sulcus. Chaetocnema babai is entirely black with strongly costate elytra while C. taiwanensis is dark brown with weakly costate elytra.

Figures

FIGURE 62. Chaetocnema taiwanensis (New status). A Holotype (female), habitus. B Head, frontal view (Holotype). C Head (frons and vertex), frontal view (Holotype). D Pronotum and peri-scutellar area (Holotype).