Holotype, ♀ (IEBR), “Vietnam: Ha Tinh, Huong Son, 18°22'N, 106°13'E, 300 m, 20.iv.–1.v.1998, Malaise [trap], AMNH, K. Long”. Paratypes: 1 ♂ (VNMN), same data, except 2–11.v.1998, Mic.739; 1 ♀ (RMNH), same data, except 900 m, 5.v.1998, Mic. 1049.

Height of head 0.7 × height of mesosoma in lateral view (Fig. 11) and its width equal to width of mesoscutum; vein m-cu of fore wing about as long as vein 2-SR+M (Fig. 12); fore wing without dark patches; vein cu-a of hind wing nearly straight (Fig. 19); scutellum punctate, without protuberance, with a more or less up curved subposterior rim remaining far below upper level of scutellum; propodeum without elevated medio-basal area (Fig. 13); apical half of hind tibia dark brown (Figs 11, 15); metasoma black dorsally and parallel-sided (Fig. 13); median carina of first tergite nearly as long as dorsal face of tergite (Fig. 13); medial area of second tergite vase-shaped (Fig. 13); median length of third tergite 1.2 × second tergite (Fig. 13); length of body 2.4–2.5 mm.

Holotype, ♀, length of body 2.4 mm, of fore wing 2.7 mm.

Head. Height of head 0.7 × height of mesosoma in lateral view (Fig. 11) and its width equal to width of mesoscutum; antennal articles 18, length of third article 1.1 × fourth segment, length of third, fourth and penultimate segments 3.3, 3.0 and 2.2 × their width, respectively (Fig. 16); maxillary palp 0.9 × height of head; malar space 0.7 × as long as basal width of mandible; length of eye in dorsal view 2.2 × temple; temple directly narrowed posteriorly (Fig. 17); POL:OD:OOL= 12:5:5; face pimply with smooth interspaces; frons shiny and smooth, vertex laterally and temple with superficial rugae (Fig. 17).

Mesosoma. Length of mesosoma 1.3 × its height; propleuron densely rugose; pronotum shiny, with some rugae and smooth posteriorly; mesopleuron densely rugose-punctate anteriorly and remainder largely smooth (Fig. 20); mesosternum shiny and moderately densely punctate; mesoscutum with satin sheen, densely punctate and notauli indicated by reticulate-punctate bands; scutellum rather convex, punctate, without protuberance, its subposterior rim slightly up curved and remaining far below upper level of scutellum; propodeum areolate and rather shiny, without elevated medio-basal area (only with small areola) or median carina (Fig. 13).

Wings. Fore wing: vein m-cu about as long as vein 2-SR+M (Fig. 12); vein 1-SR 0.35 × as long as vein 1-M; vein 1-R1 1.2 × as long as pterostigma; r:2-SR:2-SR+M = 10:10:7; vein 1-CU1 half as long as vein 2-CU1. Hind wing: vein cu-a nearly straight and its surroundings glabrous; vein M+CU about as long as vein 1-M.

Legs. Hind coxa nearly up to apex of third tergite (Fig. 14), mainly rather sparsely punctate but dorso-apically densely punctate and with some striae; length of hind femur, tibia and basitarsus 3.4, 5.2 and 4.0 × their width, respectively (Fig. 15); outer apical half of hind tibia and ventrally hind tarsus with dark brown spines; length of outer and inner spur of middle tibia 0.5 and 1.0 × middle basitarsus, respectively and inner spur curved (Fig. 11); length of outer and inner spur of hind tibia 0.5 and 0.7 × hind basitarsus, respectively and inner spur straight; tarsal claws without lobe.

Metasoma. Metasoma parallel-sided in dorsal view (Fig. 13); first tergite short, parallel-sided apically, mainly longitudinally rugulose, its median carina nearly as long as dorsal face of tergite ending in a smooth triangular area and crenulate grooves along dorsal carinae X-shaped (Fig. 13); medial area of second tergite vase-shaped, largely smooth but anteriorly superficially punctate and its surroundings coarsely longitudinally rugose (Fig. 13); third tergite coarsely irregularly rugose, but medially superficially sculptured and sublaterally depressed and medially 1.2 × longer than second tergite; ovipositor sheath 0.11 × as long as fore wing and 0.7 × hind basitarsus, narrow (Fig. 14).

Colour. Black; palpi, tibial spurs and tegula white; clypeus, mandible, galea, humeral plate, scapus and pedicellus (except brown stripe), third-fifth antennal articles ventrally, legs (but apical half of hind tibia and tarsus (except pale yellow basal 0.4 of hind basitarsus) dark brown), anterior half of metasoma ventrally, wing veins (but 1-M, 1-CU1 and cu-a brown) pale yellow; fore leg, middle leg (but coxa brown and femur yellowish-brown) and metasoma yellow; pterostigma (except basally) and fourth-seventh tergites dark brown; apex of hind femur, hypopygium and ovipositor sheath largely brown; wing membrane subhyaline.

Variation. Length of body 2.3–2.5 mm, of fore wing 2.6–2.8 mm; vein 1-R1 of fore wing 1.0–1.2 × as long as pterostigma; medial area of second tergite mainly distinctly rugose or superficially punctate. Male is very similar and has vein 1-CU1 0.6 times vein 2-CU1.

Vietnam.

Unknown. Adults collected in AprilMay.

Name derived from “nigro” (Latin for “blacken”) and “soma” (Greek for “body”) because of the mainly black body.