Trichrysis chamchuensis Wiśniowski & Nguyen, sp. nov.

Material examined. Holotype, ♀: / VIET NAM; Cao Duong, Yen Thuan / Ham Yen, Tuyen Quang, Cham Chu / NR, 16.v.2019; 691 m;/ 22°17’08.6” N, 104°59’27.4” E;/ [leg.] NTPL, NQC /

Additional material: Paratype, female, same data, and locality.

Diagnosis. Middle sized species with robust, densely punctate body and mostly golden-green colouration with some blue colour dorsally (Fig. 7). Sublateral, longitudinal carina on pronotum fully developed (Fig. 10). Tegula predominantly metallic, blue-green, outer margin partly brown. T1 and T2 bright blue dorsally, golden-green laterally and apically. T3 apically with sharp median tooth (Fig. 11); pits fused into pair of elongated holes on both sides of median keel on T3 (Fig. 12).

Description. Female. Holotype. Body length 7.0 mm. Paratype, body length 6.7 mm.

Head. Scapal basin deep and punctate, in middle part punctures partly fused forming transverse striae (Fig. 8). Brow prominent, TFC single, slightly inverted V-shaped, recurved laterally. Brow raised between TFC and scapal basin, flattened, polished medially, with elongated shallow punctures. Brow above TFC flattened, with dense punctures. BOL 1.7 × MOD. Relative length of P:F1:F2:F3=1.0:2.0:1.0:0.9; F1 l/w=3.0; OOL 1.4 × MOD; POL 1.5 × MOD; MS 1.2 × MOD; clypeal apex incised medially. Mandible without subapical tooth. Malar space with few small punctures, and with genal carina reaching up to 2/3 of head height. Setae on vertex yellowish, not longer than MOD. Ocellar triangle obtuse, densely punctured (Fig. 9).

Mesosoma. Median pronotal line moderately deep, not extending to posterior margin of pronotum. Sublateral, longitudinal carina on pronotum fully developed (Fig. 10). Punctation on pronotum, mesoscutum and mesoscutellum with variable interspaces between punctures, 0.2–1.0 × PD; interspaces shining and punctate. Mesepisternum with large punctures, interspaces narrow, 0.1–0.6 × PD. Episternal sulcus and especially scrobal sulcus with large areolate punctures, about 2.0 × as large as punctures on mesepisternum (Fig. 10). Setae on outer edge of metatibia short, not longer than the half their distal width.

Metasoma. Metasoma densely punctate; punctures smaller than on mesosoma. Interspaces on T1 and T2 0.6–1.2 × PD, polished, with only scattered tiny punctures. T1 with short median groove anteriorly, T2 with distinct median carina, reaching apex of T2 (Fig. 7). T3 punctate and wrinkled (Fig. 12); prepit bulge slightly convex (Fig. 11); pits fused into pair of elongated holes on both sides of median keel (Fig. 12). Median tooth on apex of T3 sharp and pointed, lateral teeth shorter (Fig. 12). Interval between median tooth and lateral tooth broadly incurved. All sterna in both holotype and paratype are partly destroyed ventrally, and black spots cannot be therefore described .

Colouration. Body metallic golden green, with blue reflections on pronotum and laterally on mesosoma. T2 dorsally blue, laterally, and apically golden green. Small blue spots medially on pronotum, mesoscutum and mesoscutellum. Ocellar triangle with greenish interspaces. Scape, pedicel and only base of F1 metallic green, rest of flagellum black. Tegula predominantly metallic, blue-green, outer margin partly brown. Wings slightly dimmed. Legs metallic bright green, basitarsi greenish, rest of tarsi blackish.

Male. Unknown.

Distribution. North-eastern Vietnam (Tuyen Quang Province).

Remarks. Trichrysis chamchuensis sp. nov. is similar to T. pellucida (du Buysson, 1887) and T. yuani Rosa, Feng & Xu, 2016 but is easy distinguishable by unique shape of pits of the pit row fused into pair of elongated holes on both sides of median keel on T3 (versus at most partly separated pits in both T. pellucida and T. yuani), T3 with sharp median tooth (versus blunt in T. yuani), pedicel and F1 basally greenish (versus black in T. pellucida), and mostly golden-green body colour (versus usually dark blue in T. pellucida and light blue in T. yuani).

Etymology. The specific name is an adjective derived from Vietnamese name of the ‘Cham Chu’ protected area, where the specimens were collected.