A new species of Acetalius Sharp from eastern China (Coleoptera, Staphylinidae, Pselaphinae)

Abstract The genus Acetalius Sharp currently contains two species from Japan. In this paper, a third species, Acetalius grandis Yin & Li, sp. n., is described from eastern China. The foveal pattern of Acetalius, and polymorphism and major diagnostic features of Acetalius grandis are figured. An updated key to Acetalius species is provided.


Introduction
The genus Acetalius Sharp was originally described from a single species, A. dubius Sharp, based on a male collected from leaf litter in Kyushu (Suwa Shrine), Japan (Sharp 1883). The specific epithet (dubius means 'doubtful, dubious') reflected the author's uncertainty about the higher placement of this genus, by stating that the new species has a 'Pselaphini-like hind body' and an 'elongate Euplectus head'. Since the original description, Acetalius has been historically placed in the tribe Brachyglutini (Raffray 1903(Raffray , 1904a(Raffray , 1904b(Raffray , 1904c(Raffray 1908(Raffray , 1911, in its own tribe Acetaliini (Jeannel 1958), or together with Philoscotus Sawada in subtribe Acetaliina of Euplectini (Besuchet 1985, Nomura 1988a, Newton and Chandler 1989. Recently, Chandler (2001) restricted the concept of Euplectini, removed all taxa having visible tergites IX and sternite IX to the Trichonychini, and placed Acetaliina as a junior synonym of Panaphantina. Besuchet (1985) redescribed A. dubius and added a second species, A. pilosus Besuchet, based on a single male from Shikoku. Thereafter, both species of Acetalius were treated by Nomura in a series of papers (Nomura 1988a, b, c) revising the subtribe Acetaliina. Thus Acetalius is so far represented by two species confined to Japan (Nomura 2013). Members of Acetalius lack distinct abdominal paratergites, which are reduced to pairs of marginal carinae, and lack the lateral metacoxal foveae that are often present in other genera of Panaphantina. During our investigation of the pselaphine fauna of eastern China, a third species of Acetalius was recognized among the material collected from Fengyangshan Nature Reserve, Zhejiang, which is described in this paper. The entire foveal pattern of Acetalius is investigated and described on the basis of a disarticulated male paratype on a slide preparation.

Material and methods
The type material treated in the present paper is deposited in the Insect Collection of the Shanghai Normal University (SNUC).
Dissected parts were preserved in Euparal mounting medium on a plastic slide that was placed on the same pin with the specimen. To investigate the foveal pattern, a male paratype was completely disarticulated and preserved on a slide preparation. Habitus images were taken using a Canon 5D Mark III camera in conjunction with a Canon MP-E 65mm f/2.8 1-5X Macro Lens and a Canon MT-24EX Macro Twin Lite Flash. Images of the morphological details were made using a Canon G9 camera mounted on an Olympus CX31 microscope. Line drawings were initially produced using an Olympus U-DA Drawing Tube, and then inked in Adobe Illustrator CS5. Zerene Stacker version 1.04 was used for image stacking. All images were modified and grouped in Adobe Photoshop CS5 Extended.
The collecting data of the material are quoted verbatim, information not included on the label is placed in parentheses. A slash is used to separate different labels.
The following abbreviations are applied: AL -length of the dorsally visible part of the abdomen (posterior to elytra) along the midline; AW -maximum width of the abdomen; EL -length of the elytra along the suture; EW -maximum width of the elytra; HL -length of the head from the anterior clypeal margin to the occipital constriction; HW -width of the head across the eyes; PL -length of the pronotum along the midline; PW -maximum width of the pronotum. Length of the body (BL) is a combination of HL + PL + EL + AL. Diagnosis. Body large-sized, 1.85-2.23 mm; frons with a Y-shaped carina extending anteriorly to reach clypeal anterior margin; each eye of macropterous male with about 55 facets, that of apterous male with about 25-30 facets, and apterous female about 12 facets; antennomeres III elongate, IV-X distinctly transverse; abdominal tergite IV with three pairs of marginal carinae, discal carinae parallel; sternite IV with long median and two shorter admesal carinae.