Lathrobium bisinuatum Assing & Zhong Peng 2013

Small species without sexual size dimorphism. Body length 5.2–6.5 mm; length of forebody 2.6–2.8 mm. Habitus as in Fig. 2F. Coloration: body dark-brown to blackish-brown, abdominal apex indistinctly paler; legs and antennae reddish. Pronotum moderately slender, 1.21–1.26 times as long as broad. Posterior margin of tergite VIII truncate to weakly convex in both sexes. Other external characters as in Lathrobium hastatum. Male. Sternites III-VI unmodified. Sternite VII strongly transverse, symmetric, with shallow median impression posteriorly, this impression with sparse and unmodified pubescence; posterior margin weakly and broadly concave (Fig. 8D). Sternite VIII moderately transverse, symmetric, shallowly impressed along the middle, this impression posteriorly with cluster of dense modified black setae on either side of middle; posterior excision very shallow, posterior margin on either side of this impression weakly concave (Fig. 8E). Sternite IX as in Fig. 8F. Aedeagus (Figs 8G, H) 0.9-1.0 mm long; ventral process laterally compressed, rather short, subapically curved, and apically acute; apical portion of dorsal plate of conspicuous shape, very long and slender, bisinuate in lateral view, and considerably projecting beyond apex of ventral process apically; basal portion of dorsal plate very short; internal sac with small and weakly sclerotized basal sclerite and with additional, semi-transparent apical sclerite. Female. Sternite VIII 0.8–0.9 mm long, weakly oblong, posterior margin distinctly produced in the middle, apex of this projection truncate to weakly convex (Fig. 8B). Tergite IX undivided in the middle, with long median portion, and with relatively short postero-lateral processes; tergite X much shorter than tergite IX in the middle (Fig. 8C).

Like the other species described above, Lathrobium bisinuatum is probably endemic to the Emei Shan, where it was found primarily at high altitudes (2,500–3,000 m). In one locality at 2,500 m, Lathrobium bisinuatum was found together with Lathrobium iunctum and Lathrobium hastatum. Four females were collected somewhere between 1,800–2,400 m; they have the same label data as specimens of Lathrobium iunctum, Lathrobium coniunctum, and/or Lathrobium hastatum, suggesting that they were collected syntopically. Some of the specimens were sifted from rhododendron litter and humus in a rhododendron forest on a west slope near the mountain summit at an altitude of 2,800–3,035 m (Fig. 12).