Five new apterous species of the genus Lathrobium Gravenhorst (Coleoptera, Staphylinidae, Paederinae) from the Baishanzu Natural Reserve, East China

Abstract Five new apterous species of the genus Lathrobium Gravenhorst, 1802 from Baishanzu Natural Reserve, Zhejiang, East China, Lathrobium baishanzuense sp. n., Lathrobium immanissimum sp. n., Lathrobium obstipum sp. n., Lathrobium pilosum sp. n. and Lathrobium tangi sp. n., are described and illustrated. The Lathrobium fauna of the study region is represented by two distinct lineages.


Introduction
Up to date, 57 species of the genus Lathrobium Gravenhorst have been reported from mainland China, eleven of which are known from Zhejiang Province (Peng et al. 2012a, b;Watanabe 1999a, b;Watanabe and Luo 1992). Baishanzu is a nature reserve situated in Longquan and Qingyuan counties in southwestern Zhejiang province, eastern China. Medium mountain and hill areas constitute the main landform of the nature reserve and the dominant types of vegetation are evergreen broad-leaved forests and mixed coniferous and broad-leaved forests.
In 2004 and 2008, our colleagues conducted two expeditions to Baishanzu and collected numerous Lathrobium specimens from the floor of hardwood forest by sifting moist to wet leaf litter and humus (Tang pers. comm.).
Five apterous species were identified. Based on the morphology and chaetotaxy of the male sexual characters, they belong to two different species groups.

Material and methods
The following abbreviations are used in the text, with all the measurements in millimeters: BL length of body from the anterior margin of the labrum to the apex of the abdomen; FL length of forebody from the anterior margin of the clypeus to the posterior margin of the elytra; HL length of head from the anterior margin of the clypeus to the posterior margin of the head; HW maximum width of head; PL length of pronotum along midline; PW maximum width of pronotum; EL length of elytra from the apex of the scutellum to the posterior margin of the elytra.
Elytra with punctation denser than that of pronotum and well defined; hind wings completely reduced.
Male. Sternite V (  Distribution. East China: Donggong mountain range. Etymology. The specific epithet is derived from the type locality "Baishanzu". Comparative notes and comments. Two distinct species groups occur in Baishanzu. One of these groups includes L. baishanzuense, the three following species from Baishanzu, and additionally L. daicongchaoi Peng & Li, 2012  The species group is characterized by a male sternite V with a posteromedian impression with dense dark setae and male sternites III-IV with conspicuously modified setae in the posterior or postero-median impression in some species, evident synapomorphies constituting the monophyly of this species group. These characters appear to be unique among Chinese Lathrobium.
Among the species of this group, L. baishanzuense is characterized particularly by the conspicuous modifications of the male sternite VIII and the morphology of the aedeagus. Habitus as in Fig. 1B. General appearance similar to that of L. baishanzuense, except for the much broader and larger body, the narrow impunctate midline on the pronotum and coarser punctation on the head, pronotum and elytra.
Distribution. East China: Donggong mountain range. Etymology. The specific epithet (superlative of the Latin adjective immanis: huge) alludes to the size of the aedeagus.
Comparative notes. The new species is readily distinguished from all eastern Chinese Lathrobium species by the large size and stout habitus, and by the presence of dense dark setae in the small posterior impression of sternite III. Comparative notes. This species is close to L. tangi sp. n. in sharing a large impression on the male sternite IV and a similar shape of the male sternite VII. In L. pilosum, the posterior margin of the male sternite VI has several point-like setae, and male sternite VIII is symmetrically emarginate.  Habitus as in Fig. 2A. Similar to L. baishanzuense, except for the darker coloration of body, the somewhat larger body size, slightly coarser and sparser punctation on the head and pronotum, and weakly convex lateral margins of pronotum in dorsal view.
Female. Posterior margin of tergite VIII (Fig. 6A) convex; sternite VIII ( Fig. 6B) longer than that of male, middle of apical margin with apically convex projection; tergite X (Fig. 6F) convex apically, longer than tergite IX in the middle, but not reaching anterior margin of tergite IX (Fig. 6F).
Distribution. East China: Donggong mountain range. Etymology. The species is named after Liang Tang, who collected the type seris. Comparative notes. Lathrobium tangi is similar to L. pilosum large impression on the male sternite IV and a similarlyshaped male sternite VII. In L. tangi, the posterior margin of the male sternite VI is unmodified and the male sternite VIII has an asymmetric emargination.   Female. Posterior margin of tergite VIII (Fig. 7A) weakly convex; sternite VIII ( Fig. 7C) longer than that of male, posterior margin strongly convex; tergite X ( Fig.  7B) convex apically, not reaching anterior margin of tergite IX (Fig. 7B).
Distribution. East China: Donggong mountain range. Etymology. The specific epithet (Latin, adjective: awry) alludes to the chaetotaxy of the male sternite VIII.
Comparative notes and comments. The new species is similar to L. sheni Peng & Li, 2012 from Jiulongshan in having similarly shaped male sternites VII and IX. The new species can be distinguished from L. sheni by a cluster of short setae on the posterior margin of the male sternite VIII and the distinctly flattened aedeagus. In L. sheni, the male sternite VIII has two rows of dense setae and the aedeagus is stout.
Lathrobium obstipum evidently represents a different lineage than the other species recorded from Baishanzu, since it does not share their derived modifications of the anterior male sternites. It is additionally distinguished from them by the smaller body, yellowish brown legs, the unmodified male sternite III-VI, the nearly truncate posterior margin of the male sternites VII and VIII, and the distinctly flattened aedeagus without a sclerotized dorsal plate.