Description of Pella tianmuensis sp. n. from eastern China (Coleoptera, Staphylinidae, Aleocharinae)

Abstract Pella tianmuensis sp. n., a myrmecophile associated with Lasius (Dendrolasius) spathepus Wheeler, 1910 in West Tianmushan Natural Reserve, Zhejiang, is described, illustrated and distinguished from its congeners.


Introduction
The genus Pella Stephens, 1833 was previously represented by 63 species (Hlaváč et al. 2011, Song and Li 2013, Zheng and Zhao 2014, nine of which have been reported from China. In 2014, our team surveyed the staphylinid fauna of the West Tianmushan (Zhejiang, East China), and collected a series of an unidentified Pella species from a colony of the species of Lasius (Dendrolasius) spathepus Wheeler, 1910. An examination of this material revealed that the Pella species was undescribed.

Material and methods
Specimens were killed with ethyl acetate and preserved in 75% ethanol before dissection. Photos of the habitus were taken with a Canon EOS 70D with an MP-E 65 mm macro photo lens. Head length was measured from the clypeal anterior marginto the occipital constriction; elytral length at the suture from the apex of the scutellum to the elytral posterior margin.
The following abbreviations are used in the text: BL-body length, from the anterior margin of the labrum to the abdominal apex of tergite VIII; FBL-forebody length, from the clypeal anterior margin to the posterior margin of elytra; PL-length of the pronotum along midline; HW-width of the head across the eyes; PW-maximum width of the pronotum; EL-length of elytra from the apex of the scutellum to the posterior margin of the elytra; EW-maximum width of the elytra; SL-length of elytral suture.
All the types are deposited in the Insect Collection of Shanghai Normal University, Shanghai, China (SNUC).
Head (Fig. 1A) widest anteriorly; surface finely reticulate, covered with short golden setae; antennomeres VI-X distinctly transverse (Fig. 1B). Pronotum (Fig. 1A) 1.28 times as wide as long and 1.40 times as wide as head; widest approximately in anterior third, narrowed posteriorly; surface covered with short golden setae; hypomera fully visible in lateral view. Elytra (Fig. 1A) approximately 1.08 times as long as pronotum; covered with short golden setae; humeral angle with one macroseta. Hind wings fully developed. Abdomen (Fig. 1A) widest at segments III-IV; surface with transverse microsculpture.
Female: Tergite VIII (Fig. 1D) with posterior margin truncate and weakly crenate; sternite VIII ( Fig. 1F) with 12 or 13 pairs of macrosetae. Spermatheca (Fig. 1G)   Biological notes. Most material of the new species was taken by sifting mixed leaf litter around the nest of Lasius (Dendrolasius) spathepus, together with three species of Homoeusa Kraatz, 1858 and with Dendrolasiophilus monstrotibialis (Hlaváč, Sugaya & Zhou, 2002). At least three Pella and some Homoeusa beetles were observed walking along the ant trails. Approximately five Pella individuals were observed eating dead caterpillars together with Lasius workers.
Remarks. Based on the size of eyes, the shapes of the pronotum, the bicolored elytra, and the morphology of the aedeagal median lobe, Pella tianmuensis belongs to the P. cognata group, of which four species are known from China: P. kishimotoi Maruyama, 2006, P. sichuanensis Zheng & Zhao, 2014, P. puetzi Assing, 2009, and P. maoershanensis Song & Li, 2013. The new species is distinguished from P. kishimotoi by the broader and shorter ventral process of the aedeagus in ventral view; from P. sichuanensis by the darker color of the body, and by the length of the elytra slightly exceeding that of the pronotum (P. sichuanensis: EL/PL= 0.86); from P. puetzi and P. maoershanensis by the absence of a sexual dimorphism of the head and the different shape of the ventral process of the aedeagus, especially in lateral view.
Etymology. The specific epithet is derived from the type locality.