First record of Arthromelodes Jeannel in China, with description of a new species (Coleoptera, Staphylinidae, Pselaphinae)

Abstract A new species of Arthromelodes Jeannel, A. choui sp. n., is described from northern Taitung, Taiwan, representing the first record of the genus in China. The species is distinctive, and may be readily separated from its congeners by the unique structures of male tergite 1(IV), and the aedeagus.


Introduction
The genus Arthromelodes Jeannel of the pselaphine tribe Batrisini is a group of modest size containing 21 species and subspecies distributed in Japan (20 spp.) and Vietnam (1 sp.) (Jeannel 1954(Jeannel , 1957(Jeannel -1958Nomura 1991;Arai 2002). This genus was included in Jeannel's fifth division of the Batrisina (Jeannel 1958(Jeannel , 1959) and Nomura's 'Batrisocenus complex of genera' (Nomura 1991) of Asian Batrisini, where members share a median and a pair of lateral longitudinal sulci, and a complete transverse antebasal sulcus on the pronotum, the lack of lateral or discal spines on the pronotum, the presence of two basal foveae on each elytron, and an elongate abdominal tergite 1(IV). Arthromelodes resembles Batrisocenus Raffray (also Physomerinus Jeannel and Batriscenaulax Jeannel) and Batrisceniola Jeannel in most external features (probably due to extensive homoplasy of characters), and under current definition may be separated from the former only by the aedeagus with a moderately developed basal capsule (capsule is strongly reduced in Batrisocenus; e.g., Chandler 2001: 264), and from the latter by the lack of a median bunch of erect setae on tergite 4(VII) (bunched setae are present on tergite 4 in both sexes of Batrisceniola; e.g., Yin and Li 2014). Within Arthromelodes, species are usually easy to determine thanks to the distinct sexual modifications of the male metatibiae (usually present), and of abdominal tergites 1(IV) and 4(VII).
(2 specimens), and a new species of Arthromelodes (8 specimens), representing the first record of this genus in China, which is described and compared to similar congeners here.

Materials and methods
The type series is deposited in the Insect Collection of the Shanghai Normal University, Shanghai, China (SNUC), and the National Museum of Natural Science, Taichung, Taiwan (NMNS). The collecting data of the material are quoted verbatim; information not included on the label is placed in parentheses. Following Chandler (2001), the abdominal tergites and sternites are given Arabic numerals for visible sclerites, and Roman numerals indicate the morphological position. Habitus image ( Fig. 1A) was taken using a Canon 5D Mark III camera in conjunction with a Canon MP-E 65 mm f/2.8 1-5× Macro Lens, and a Canon MT-24EX Macro Twin Lite Flash was used as light source. Images of the morphological details ( Fig. 1B-G) were produced using a Canon G9 camera mounted on an Olympus CX31 microscope under transmitted or reflected light. Zerene Stacker version 1.04 was used for image stacking. All images were edited and grouped in Adobe Photoshop CS5 Extended. Diagnosis of male. Body length slightly more than 2 mm; metaventrite with pair of laminar projections; abdominal tergite 1(IV) with large cavity at posterior half, lateral setiferous patches composed of short setae and weakly demarcated; legs lacking modifications, except mesotibia with distinct apical spur; aedeagus with median lobe strongly curved rightwards apically, dorsal lobe erect, and strongly narrowed and curved downwards at apex.
Comments. Using the key in Nomura (1991), Arthromelodes choui would key out at couplet 9 with A. sinuatipes Nomura and A. aizuanus Nomura. These three species share the presence of a cavity on male tergite 1(IV), a nodule placed posterior to the cavity, as well as a pair of setiferous patches lateral to the cavity. Arthromelodes choui may be readily separated from A. sinuatipes by the less laterally expanded margins of tergite 1, the less demarcated setiferous patches, the sinuate anterior margin of tergal cavity, and the much less transverse basal capsule of the aedeagus; and from A. aizuanus by the much larger abdominal cavity, the broader and less demarcated setiferous patches, and much shorter basoventral projection of the aedeagus. A similar tergal cavity and nodule are also present in A. dilatatus (Raffray) (with four subspecies), but this species can be easily characterized by the distinct lateral expansions at sides of tergite 1(IV), while the new species lacks such structures. Arai (2002) described A. watanabei Arai from Honshu, Japan, and this species may be separated from A. choui by the cavity on tergite 1 being much smaller and shallower, and by the form of the aedeagus (Arai, 2002: figs 1, 6-7). According to the description and figures in Jeannel (1954: 249), A. choui may be well-separated from A. carieri Jeannel (type species of Arthromelodes) from Vietnam again by the different structures of the male tergal cavity and aedeagus.
Distribution. Southern China: Taiwan. Etymology. The specific epithet is dedicated to my friend Wen-I Chou, a Taiwanese specialist of Cerambycidae, who collected the type series of the new species.