(Figs 1B, 3, 8B)

Type locality. China, Guangxi Province, Lingui County, Huaping Natural Reserve, An-Jiang-Ping, 1400–1700 m a.s.l., 25°35′46″N, 109°55′41″E.

Type material. HOLOTYPE: J, labeled ‘ CHINA: Guangxi Prov. / Lingui County / Huaping, Anjiangping / 14.vii.2011, 1400–1700 m / Zhong Peng leg. // HOLOTYPE (red) / Labomimus quadratithorax / sp. n., Yin & Li / det. 2012, SNUC’.

Diagnosis. Reddish brown; medium-sized; postgenae strongly narrowed posteriorly; antennomeres IX–XI elongate and enlarged; pronotum nearly quadrate; with long metaventral processes; metatrochanter spinose; aedeagus with asymmetric median lobe.

Description. Male (Fig. 1B). Length 2.73. Head as long as wide, HL 0.68, HW 0.67; eyes each composed of about 20 facets. Antennal club as in Fig. 3A. Pronotum (Fig. 3B) as long as wide, PL 0.61, PW 0.61, with lateral margins slightly rounded laterally. Elytra wider than long, EL 0.68, EW 1.06. Metaventral processes long, broadened apically (Fig. 3C). Protrochanters, profemora (Fig. 3D), mesotrochanters and mesofemora (Fig. 3E) simple, metatrochanters (Fig. 3F) with short blunt ventral spine. Abdomen large, AL 0.76, AW 1.07. Sternite IX as in Fig. 3G. Aedeagus length 0.50; median lobe asymmetric at apex (Figs. 3H–J).

Female. Unknown.

Comparative notes. This species can be separated from all other congeners by the uniquely constricted postgenae and the quadrate pronotum.

Etymology. The new species is named from a combination of the Latin stem, ‘ quadrati ’ and Greek word ‘ thorax ’, referring to the unique pronotal shape of the new species. Noun in apposition.

Biology. The single specimen was collected by sifting leaf litter along a road to the peak in a broad-leaved forest (Fig. 8B).

Distribution. South China: Guangxi.