Holotype, ♀ (ZUH), “N. China: Shandong, Anqiu, Suotou Mt., 31.VII.2009, c. 120 m, Li Xi-Ying, RMNH’09”. Paratypes (RMNH): 3 ♀ + 1 ♂ with same label-data; 1 ♂, “S. China: Hunan, nr Suining, Huangsang N.R., Shaoyang, 12–13.VI.2009, 1000 m, Xi-Ying Li, RMNH’09”.

Mandible with long fine ventral carina (Fig. 84); rim of clypeus pointed downwards (Fig. 78); pronotum and mesopleuron dorsally superficially granulate;occipital carina finely crenulate; clypeus comparatively wide (Fig. 78); tegulae dark brown; propleuron rugulose subposteriorly; notauli only anteriorly distinctly impressed; precoxal sulcus wide and crenulate (Fig. 73); postpectal carina medio-ventrally coarsely developed; first discal cell of fore wing comparatively transverse (Fig. 74); vein m-cu of fore wing 5 times longer than vein 2-SR+M (Fig. 74); second metasomal tergite of ♀ granulate (Fig. 76).

Holotype, ♀, length of body 2.0 mm, of fore wing 2.1 mm.

Head. Antenna with 19 segments (incomplete; in paratypes 1.3 times as long as fore wing); length of third segment 1.2 times fourth segment, length of third and fourth penultimate segments 2.3 and 2.0 times their width, respectively (Fig. 81); length of maxillary palp equal to height of head; labial palp segments slender; occipital carina finely crenulate (Fig. 84), rather close to hypostomal carina, absent dorsally and behind upper third of eye; with distinct groove behind stemmaticum; hypostomal carina medium-sized; length of eye in dorsal view 3.0 times temple; frons medially narrowly convex between depressions behind antennal sockets, with depression between antennal sockets and laterally slightly convex, glabrous; face sparsely finely punctate, evenly convex (Fig. 78); width of clypeus 2.8 times its maximum height and 0.7 times width of face, clypeus rather flat, smooth except for some punctures and its ventral margin slightly differentiated, thin, straight and pointed downwards; hypoclypeal depression rather large (Fig. 78); malar suture present; mandible normal, slightly convex and sparsely punctate and with fine ventral carina (Fig. 79).

Mesosoma. Length of mesosoma 1.2 times its height; pronope absent (Fig. 83); pronotal side smooth, but distinctly crenulate posteriorly, superficially granulate dorsally and oblique groove finely crenulate, no ventral oblique carina (Fig. 73); propleuron rugulose subposteriorly (Fig. 73); epicnemial area largely smooth dorsally, with few crenulae anteriorly; precoxal sulcus anteriorly and medially present, wide, coarsely crenulate (Fig. 73); rest of mesopleuron smooth; pleural sulcus indistinctly crenulate dorsally and distinctly crenulate ventrally; mesosternal sulcus as a row of punctures, with strong postpectal carina medio-ventrally; notauli only anteriorly widely impressed (Fig. 75); mesoscutum smooth and only posteriorly with few setae; medio-posterior depression of mesoscutum round and small (Fig. 83); lateral margin of mesoscutum crenulate; scutellar sulcus wide and coarsely crenulate (Fig. 75); scutellum smooth and slightly convex; dorsal surface of propodeum not differentiated and with long medio-longitudinal carina, transverse carina distinct, posterior surface largely reticulate-rugose, with sublateral carinae (Fig. 76).

Wings. Fore wing (Fig. 74): pterostigma triangular; 1-R1 reaching wing apex and 1.7 times as long as pterostigma; r:3-SR:SR1 = 3:27:42; 2-SR:3-SR:r-m = 15:27:12; r short and slender; 1-M and SR1 nearly straight; m-cu postfurcal by fifth of its length; cu-a subinterstitial and 1-CU1 hardly widened; first subdiscal cell closed, CU1b short; apical quarter of M+CU1 sclerotized; first subdiscal cell of fore wing moderately long. Hind wing (Fig. 74): M+CU:1-M:1r-m = 5:4:2; cu-a slightly reclivous; m-cu absent; 1-1A curved.

Legs. Length of femur, tibia and basitarsus of hind leg 3.2, 8.0 and 4.0 times as long as wide, respectively; hind femur and tibia with long setae (Fig. 77).

Metasoma. Length of first tergite 0.9 times its apical width, its surface evenly gradually convex medially, longitudinally rugose and punctate posteriorly and with dorsal carinae separated and up to middle of tergite (Fig. 76); second suture obsolescent; second tergite as long as third tergite (Fig. 73) and densely and finely granulate-punctate with some fine striae (Fig. 76), its epipleuron slightly less sclerotized than notum; third tergite (except apically) superficially granulate and following tergites smooth; second and third tergites 0.7 times as long as metasoma after first tergite; length of setose part of ovipositor sheath 0.06 times fore wing and 0.2 times hind tibia (Figs 73, 80).

Colour. Dark brown (including tegulae and apex of antenna in paratypes); head dorsally and mesosoma black; palpi, scapus and legs (but telotarsi darkened) pale yellowish; mandible, clypeus and malar space yellowish-brown; pterostigma (but apically pale brown) and veins brown; wing membrane evenly slightly infuscate.

Molecular data. COI, 16S, 28S (CVA4255).

Variation. Length of body 1.7–2.0 mm, of fore wing 1.9–2.1 mm; antennal segments of ♀ 24 (1), 25 (1) or 26 (1) and of ♂ 24 (2); ventral rim somewhat upcurved or pointed downwards; pronotal side and second tergite dark brown or yellowish-brown; third tergite of male only superficially granulate, second tergite largely sculptured as in female or superficially granulate.

*China (Shandong, Hunan).

Unknown.

Name derived from “postpectus” (Latin for “posterior part of breast”), because of the presence of the postpectal carina.

The new species does not run well in the key by Chen and Weng (2005) because it has the second tergite granulate (the choices in the key are longitudinally striate or smooth), but if it is assumed that the sculpture is superficial and the tergite is nearly smooth then it runs to Xynobius indagatrix (Weng & Chen, 2005) comb. n.; Coleopioides postpectalis differs by having the length of the eye in dorsal view 3 times temple (4.2 times in Xynobius indagatrix), no dorsope (present), length of the hind femur about 3 times its width (4.7 times), length of first tergite 0.9 times its apical width (1.3 times), the second tergite granulate-punctate with some fine striae (smooth) and the propodeum with a median carina and areolate (densely rugose and without carina).