Holotype. China – Chongqing • ♂; glued on a card with two labels as follows: “China: Chongqing City, Shizhu County, Huangshui Town, Polaoxiang, Near Dafengbao, 30°13'04"N, 108°24'50"E, alt. 1550 m, 27.IX.2023, Xiao-Bin Song leg.” “HOLOTYPE: Paederussongi sp. n., Yang & Peng des. 2024” [red handwritten label]; SNUC. Paratypes. China – Chongqing • 1♀; Shizhu County, Huangshui Town, Polaoxiang, Near Dafengbao, 30°13'04"N, 108°24'50"E, alt. 1550 m, 27.IX.2023, Xiao-Bin Song leg; SNUC.

Measurements (in mm) and ratios: BL 8.11–9.55, FL 4.45–5.02, HL 1.49–1.52, HW 1.54–1.71, AnL: 2.94–3.31; PL: 1.54–1.72; PW: 1.59–1.68; EL: 0.95–1.02; EW: 1.55–1.60; AW: 1.73–1.79; AL: 2.25; HL/HW: 0.89–0.97; HW/PW: 0.97–1.02; HL/PL: 0.88–0.97; PL/PW: 0.97–1.02; EL/PL: 0.59–0.62; diameter of eye: 0.38–0.45.

Habitus as in Fig. 1C. Coloration: head and abdomen black; antennae brown to light brown; pronotum red; elytra black with distinctly bluish hue; legs brown with paler tarsi.

Head (Fig. 1C) transverse, widest across eyes; punctation coarse and sparse; interstices glossy. Eyes distinctly convex. Antennae slender, antennomere 4 approximately 3.4 times as long as broad and antennomere 10 nearly twice as long as broad.

Pronotum (Fig. 1C) nearly as long as broad, strongly convex in cross section; punctures slightly sparser than on head.

Elytra (Fig. 1C) trapeziform; punctation distinctly coarse, well defined, and moderately dense. Hind wings reduced. Metatarsomere I slightly shorter than combined length of metatarsomeres II and III.

Abdomen broader than elytra; punctation dense; interstices with distinctly transverse microsculpture; posterior margin of tergite VII without palisade fringe.

Male. Mandibles (Fig. 4B) each with weakly bifid molar tooth at apex. Labrum (Fig. 4B) with distinctly concave anterior margin, with U-shaped median excision and with broad lateral projection on either side. Posterior margin of tergite VIII (Fig. 4E) convex; sternite VII unmodified; sternite VIII (Fig. 4F) with deep posterior excision, this excision approximately 0.4 times as long as sternite VIII; aedeagus as in Fig. 4G–I, ventral plate asymmetric in ventral view; dorsal plate asymmetric, apically acute in dorsal view and not reaching apices of parameres; parameres asymmetric and weakly curved in lateral view; internal sac with pair of long sclerotized spines and single very short sclerotized spine.

Female. Mandibles (Fig. 4A) each with bifid molar tooth of similar shape. Labrum (Fig. 4A) with U-shaped median excision and with broad lateral projection on either side, as well as a small projection on either side of median excision. Tergite VIII (Fig. 4C) oblong, with convex posterior margin; posterior margin of sternite VIII (Fig. 4D) strongly convex.

The type locality is in northeastern Shizhu, eastern Chongqing. The specimens were sifted from moist leaf litter and roots in a secondary deciduous forest with bamboo at an altitude of 1550 m (Song pers. comm.). The paratype is teneral.

The species is named after Xiao-Bin Song, who collected the type specimens. He is a renowned specialist on mainly Palaearctic Paussinae.

The external and particularly the male sexual characters leave no doubt that this species belongs to the P.biacutus group. Among the species of this group, it appears to be most closely allied to P.sinisterobliquus Li, Zhou & Solodovnikov, 2013, with which it shares the similar morphology of the aedeagus. It is distinguished from P.sinisterobliquus by slightly larger body size, by the stouter pronotum, by three distinctly sclerotized spines of the internal sac and the larger parameres of the aedeagus, as well as by the shape of the female sternite VIII.