Holotype. China – Hubei Prov. • ♂; glued on a card with two labels as follows: “China: Hubei Prov., Wufeng County, Houhe N.R., 30°11'53"N, 110°35'40"E, alt. 1480 m, 12.V.2020, Wen-Xuan Bi leg.” “HOLOTYPE: Paederustrispinosus sp. n., Yang & Peng des. 2024” [red handwritten label]; SNUC. Paratypes. China – Hubei Prov. •4 ♂♂, 2 ♀♀; Wufeng County, Houhe N.R., 30°11'53"N, 110°35'40"E, alt. 1480 m, 12.V.2020, Wen-Xuan Bi leg; SNUC • 1 ♂; Wufeng County, Houhe N.R., 30°05'10"N, 110°33'04"E, alt. 1150 m, 30.IV.2004, Li-Zhen Li leg; SNUC.

Measurements (in mm) and ratios: BL 9.11–9.67, FL 4.56–4.91, HL: 1.35–1.54; HW: 1.49–1.69; AnL: 3.08–3.22; PL: 1.49–1.67; PW: 1.50–1.67; EL: 1.00–1.10; EW: 1.47–1.54; AW: 1.67–1.74; AL: 2.14–2.17; HL/HW: 0.90–0.93; HW/PW: 0.99–1.02; HL/PL: 0.90–0.93; PL/PW: 0.97–1.01; EL/PL: 0.65–0.68; diameter of eye: 0.38–0.43.

Habitus as in Fig. 1D. Coloration: head and abdomen black; antennae brown, sometimes antennomeres 4−8 infuscate; pronotum red; elytra black with distinctly bluish hue; legs with brown femora, and with brown to light brown tibiae and tarsi.

Head (Fig. 1D) transverse, widest across eyes; punctation coarse and sparse; interstices glossy. Eyes distinctly convex. Antennae slender, antennomere 4 approximately 3.3 times as long as broad and antennomere 10 1.8 times as long as broad. Mandibles (Fig. 5A, B) each with apically bifid molar tooth, without evident sexual dimorphism.

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

Elytra (Fig. 1D) trapeziform; punctation distinctly coarse, defined and moderately dense. Hind wings reduced. Metatarsomere I as long as combined length of metatarsomeres II and III.

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

Male. Labrum (Fig. 5B) with distinctly concave anterior margin, with U-shaped median excision and with large lateral projection on either side, as well as indistinct projection on either side of median excision. Posterior margin of tergite VIII (Fig. 5E) strongly convex; sternite VII unmodified; sternite VIII (Fig. 5F) with deep posterior excision, this excision approximately 0.3 times as long as sternite VIII; aedeagus as in Fig. 5G–I, ventral plate long and apically acute in ventral view; dorsal plate asymmetric and strongly sclerotized, with obtusely acute apical portion and not reaching apices of parameres; parameres distinctly asymmetric and apically straight in lateral view; internal sac with three distinctive sclerotized spines.

Female. Labrum (Fig. 5A) 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. Posterior margin of tergite VIII (Fig. 5C) weakly convex; posterior margin of sternite VIII distinctly trifurcate as in Fig. 5D.

The species was found in two localities in the Houhe Natural Reserve, to western Wufeng, Hubei. Some specimens were sifted from leaf litter, grass roots and the soil along a forest path at an altitude of 1480 m (Fig. 11).

The specific epithet of this new species consists of the Latin suffix tri- (which means “three”) and the Latin adjective spinosus (which means “spiny”). The name (a Latin adjective) refers to three distinctive sclerotized spines in the internal sac of the aedeagus.

The external and particularly the male sexual characters leave no doubt that this species belongs to the P.biacutus group. This new species is distinguished from other species of this group by the shape of female tergite VIII and the morphology of the aedeagus (the distinctly asymmetric dorsal plate and parameres, as well as two long sclerotized spines and one hooked sclerotized spine in the internal sac).