Description of Pella maoershanensis sp. n. (Coleoptera, Staphylinidae, Aleocharinae) associated with Lasius spathepus from Guangxi, South China

Abstract Pellamaoershanensis Song & Li, sp. n., collected from a colony of Lasius (Dendrolasius) spathepus in Maoershan Natural Reserve, Guangxi, is diagnosed, described and illustrated. The discovery represents the first record of the genus in South China.


Introduction
According to the latest catalogue of Lomechusini (Hlaváč et al. 2011), the genus Pella Stephens contains 61 species worldwide, among which seven are known from China: P. beijingorum Pace (Beijing), P. cooterorum Maruyama (Beijing, Yunnan), P. hlavaci Maruyama (Beijing), P. jureceki Dvořák (Beijing), P. kishimotoi Maruyama (Hunan), P. puetzi Assing (Yunnan) and P. zhoui Maruyama (Beijing). Members of Pella are com-monly found in association with the ant genus Lasius Fabricius (Maruyama 2006). Recently, the senior author and his colleagues surveyed the staphylinid fauna of the Maoershan Mountain (Guangxi, South China), and collected a large series of an unidentified aleocharine beetle by sifting leaf litter near a nest of Lasius (Dendrolasius) spathepus. A closer examination of this material revealed a new species of the genus Pella. In this paper we describe the new species, provide illustrations of its major diagnostic features, and briefly discuss the biology.

Meterials and methods
Specimens were killed with ethyl acetate and preserved in 75% ethanol before dissection; Photos of habitus were taken with a Canon EOS 50D with an MP-E 65mm Macro Photo Lens.
Head length was measured from the clypeal anterior margin to the occipital constriction; elytral length at the suture from the apex of the scutellum to the elytral posterior margin.
All the types were deposited in the Insect Collection of Shanghai Normal University, Shanghai, China (SNUC). Diagnosis. Pella maoershanensis shares with P. puetzi a similar form of male sexual character on the head (Assing 2009). The two species can be readily distinguished by the smaller body size, the distinctly transverse antennomeres VI-X, and different forms of the aedeagal distal crest and ventral process in P. maoershanensis. The new species is also similar to the other species of the P. cognata group in general appearance (Maruyama 2006) but can be readily separated by the sexually modified head in the male.
Description. Body (Fig. 1A) length: 5.5-5.8 mm. Coloration: fore body brownish; abdomen blackish, with the posterior margins of the segments reddish-brown; leg and antennae reddish-brown. Head (Fig. 1A) almost 1.2 times as wide as long; widest just behind eyes; surface finely reticulate, covered with short golden setae. Antennae (Fig. 1D) about 2.2 mm long, shorter than head, pronotum and elytra combined; antennomeres VI-X distinctly transverse. Pronotum (Fig. 1E) 1.35 times as wide as long and 1.37 times as wide as head; widest around anterior third, narrowed posteriorly; posterior margin almost rounded; covered with short golden setae, with six macrosetae; hypomera fully visible in lateral view. Elytra (Fig. 1A) about 1.9 times as long as pronotum; covered with short golden setae; humeral angle with one macrosetae. Hind wings fully developed. Abdomen (Fig. 1A) widest at segments IV-V; surface with transverse microsculpture.
Female. Posterior margin of head indistinctly angled at middle (Fig. 1C); tergite VIII ( Fig. 1G) and sternite VIII (Fig. 1I) distinctly shorter than that of male; spermatheca as in Fig. 1M.  (Figs 2A, B). Biological notes. Species of Pella are usually observed walking around the host's nest but never appear in it (Maruyama 2006). All individuals of the new species, plus three other aleocharine species were taken by sifting mixed leaf litter around the ant nest (Fig. 2C). Three possible larvae of the new species were taken back to the lab, and were observed to feed on a dead worker of the host ant (Fig. 2D). It's worth a note that two males and a female of an undescribed Dendrolasiophilus Nomura species (Yin pers. comm.) were directly collected from the deep site of the nest.
Etymology. Named after the type locality.
ant. We thank Munetoshi Maruyama and an anonymous reviewer for the critical comments on the manuscript. This study is supported by the National Science Foundation of China (No. 31172134) and Shanghai Normal University (Sk201242).