Chaetocnema (Chaetocnema) sabahensis Ruan & Yang & Konstantinov & Prathapan & Zhang 2019, New Species

35. Chaetocnema (Chaetocnema) sabahensis Ruan, Konstantinov & Yang, New Species (Fig. 56) Etymology: This species is named after the type locality. Specific epithet is a noun in apposition. Distribution: Malaysia, Singapore. Host plants: Unknown. Diagnosis: This species resembles C. hainanensis by the following characters: a distinct ridge present on each side of aedeagus on ventral side, in lateral view, aedeagus is strongly curved near apex and base, while straight at middle. However, they can be distinguished by the difference in shape of the body and aedeagus. This species also resembles C. luisiadae from Bagaman Islands in the Louisiade Archipelago [Papua New Guinea], however, it differs from the latter by narrower frontal ridge and sinuated base of pronotum. The female of Chaetocnema sabahensis is rather unique among the Oriental species of the genus in having a trilobed (usually simple in other species) last abdominal ventrite (Fig. 56 J). Description: Body length (excluding head): 1.85–2.10 mm, body width 1.10–1.20 mm. Ratio of elytron length (along suture) to width (maximum): 2.40–2.50. Ratio of pronotum width (at base) to length: 1.60–1.70. Ratio of length of elytron to length of pronotum (along middle): 2.30–2.40. Ratio of width of elytra at base to width of pronotum at base (in middle of humeral calli): 1.00–1.05. Ratio of maximum width of elytra to maximum width of pronotum: 1.20–1.30. Dorum coppery to bronzy. Antennomeres 1–6 completely yellow, 7–11 dark yellow to light brown. Tibiae and tarsi yellow. Pro- and mesofemora dark yellow. Metafemora dark brown. Head hypognathous. Frontal ridge narrow and convex. Ratio of width of frontal ridge to width of antennal socket: 1.10–1.20. Frontolateral sulcus present. Suprafrontal sulcus not deep, obcordate. Orbital sulcus deep. Number of punctures on vertex: 4–6 on each side near eye. Vertex evenly and minutely granulose. Number of punctures on orbit: 2–3 on each side. Punctures on orbit close to each other, forming a short longitudinal row. Number of punctures on frons (triangular area surrounded by frontolateral sulcus and clypeus): 0. Number of setae on clypeus: approximately 20. Number of setae on labrum: 6. Anterior margin of labrum straight or 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, long, oblique, protruding antero-laterally. Posterolateral prothoracic callosity poorly developed. Diameter of pronotal punctures 1.5 to 3 times smaller than distance between them. Elytra with convex lateral sides. All rows of elytral punctures regular and single. Interspaces between striae of punctures smooth and glabrous. Number of rows of minute punctures on each interspace: 1–2. Elytral humeral callus well developed. Width of elytral base equal to or slightly exceed width of pronotal base. First male protarsomere slightly larger than second. First and second male protarsomeres, length to length ratio: 1.00–1.05. First male protarsomere, length to width ratio: 0.95–1.10. First male protarsomere, width at apex to width at base ratio: 1.90–1.95. Excavation on metatibia moderately deep. Large lateral denticle on metatibia sharp. Metatibial serration proximal to large lateral denticle absent. First male metatarsomere, length to width ratio: 3.40–3.50. Aedeagus widening towards apex in ventral view. Ventral longitudinal groove poorly developed. Two ridges (sometimes obscure) present along lateral sides of ventral longitudinal groove. Apical denticle in ventral view long and prominent with widely rounded tip. Apical denticle in lateral view strongly curved dorsally. Minute transverse wrinkles absent on ventral side. Aedeagus in lateral view unevenly curved, sinusoidal near apex. Maximum curvature in lateral view situated apically. Spermathecal receptacle oblong-flask shaped. Basal part of spermathecal duct straight. Spermathecal pump much shorter than receptacle, with thin, acute apex. Receptacle basally much wider than apically. Apex of vaginal palpus subtriangular, with lateral margin slightly convex. Anterior end of anterior sclerotization somewhat flattened. Posterior sclerotization longer than wide. Width of posterior sclerotization greater than that of anterior. Type: Holotype: ♂, (USNM): 1) Malaysia, Sabah, Tanjung Aru Beach, 8.VIII.1983, leg. G. F. Hevel & W. E. Steiner. 2) Holotype. 3) Chaetocnema sabahensis sp. nov. des. Ruan, 2015. Paratypes: 3♂ 5♀ (USNM), Malaysia, Sabah, 3–12.VIII.1983, leg. G. F. Hevel & W. E. Steiner; 1♀ (USNM), Malaysia, Sarawak, Bako National Park, 28.IX.1966, J. F. G. Clarke; 1 (BMNH), 1) Sarawak (Malaysia): 4 th Division, Gn. Mulu NP., 2) nr. Base Camp 50–100m, 4) Malaise trap, ix–77, 5) Chaetocnema sp., 6) Paratype, 7) Chaetocnema sabahensis sp. nov. Des. Ruan, Konstantinov & Yang, 2016; 1♂ 2 (BMNH), 1) Seliliw, 16.9.22, 2) Singapore, C. J. Saunders, B.M. 1933–227, 3) Paratype, 4) Chaetocnema sabahensis sp. nov. Des. Ruan, Konstantinov & Yang, 2016; 2 (BMNH), 1) B.7im.Rd.8, 9.7.22, 2) Singapore, C. J. Saunders, B.M. 1933–227, 3) Paratype, 4) Chaetocnema sabahensis sp. nov. Des. Ruan, Konstantinov & Yang, 2016; 2 (BMNH), 1) Reg.W., 12.8.22, waterside, 2) Singapore, C. J. Saunders, B.M. 1933–227, 3) Paratype, 4) Chaetocnema sabahensis sp. nov. Des. Ruan, Konstantinov & Yang, 2016; 1 (BMNH), 1) Res.S. (W), jungle, 8.4.23, 2) Singapore, C. J. Saunders, B.M. 1933–227, 3) Paratype, 4) Chaetocnema sabahensis sp. nov. Des. Ruan, Konstantinov & Yang, 2016; 2 (BMNH), 1) Reg.W., 12.8.22, waterside, 2) Singapore, C. J. Saunders, B.M. 1933–227, 3) Paratype, 4) Chaetocnema sabahensis sp. nov. Des. Ruan, Konstantinov & Yang, 2016; 1 (BMNH), 1) Singapore, C. J. Saunders, B.M. 1933–227, 2) Paratype, 3) Chaetocnema sabahensis sp. nov. Des. Ruan, Konstantinov & Yang, 2016.Published as part of Ruan, Yongying, Yang, Xingke, Konstantinov, Alexander S., Prathapan, Kaniyarikkal D. & Zhang, Mengna, 2019, Revision of the Oriental Chaetocnema species (Coleoptera, Chrysomelidae, Galerucinae, Alticini), pp. 1-206 in Zootaxa 4699 (1) on pages 95-97, DOI: 10.11646/zootaxa.4699.1.1, http://zenodo.org/record/354303