Description of a new Pselaphodes Westwood (Coleoptera: Staphylinidae: Pselaphinae) from Vietnam

Abstract Background A new species of the genus Pselaphodes Westwood, P. fansipanensis Bekchiev & Yin sp. n., is described from northern Vietnam. The unique modification of the antennomeres 9–10 of the male readily separates the new species from all known congeners. New information New Pselaphodes species from Vietnam


Introduction
The Pselaphinae (Coleoptera: Staphylinidae) fauna of Vietnam is poorly studied. Until now, 112 species (Bekchiev 2010, Nomura 2013, Nomura and Pham 2019 have been known from the country. The diversity of habitats and environmental conditions in Vietnam implies that the diversity of pselaphine fauna may be much greater. A total of 65 species of Pselaphodes (Tyrini) have been described, all from the Oriental region -China, Nepal, India, Sri Lanka, Thailand, the Philippines and East Malaysia (see Huang et al. 2018 for checklist and distributional map) and two additional unnamed species were recently reported from Vietnam (Nomura and Pham 2019).
In September 2018, a short expedition to southern and northern Vietnam was organised by the Institute of Ecology and Works Protection (Hanoi) and the National Museum of Natural History (Sofia), giving the opportunity to collect rich zoological material. One of the visited localities was Fansipan Mountain and, especially, the Fansipan Summit. It is the highest (3,143 metres a.s.l.) mountain in the Indochinese Peninsula (including Vietnam, Laos and Cambodia), hence its nickname "the Roof of Indochina". Included in the material was a new Pselaphodes species, which is described below.

Materials and methods
The material was collected in an open habitat with shrubs and grasses ( Fig. 1) by soil and litter sifting.
Specimens were examined by Zeiss Stemi 2000C stereo-microscopes. Male genitalia and other dissected parts were studied using a Zeiss transmitted-light microscope at magnifications up to 500x. Genital segments were dissected and treated with potassium hydroxide (KOH). The dissected parts were mounted in Euparal and pinned with the relevant specimen.
The following acronyms are used in the text: BL-length of the body (= HL + PL + EL + AL); HL-length of the head from the anterior clypeal margin to the occipital constriction; HW-width of the head across eyes; PL-length of the pronotum along the midline; PWmaximum width of the pronotum; EL-length of the elytra along the suture; EW-maximum width of the elytra; AL-length of dorsally visible part of the abdomen along the midline; AW-maximum width of the abdomen; NMNHS -National Museum of Natural History, Sofia, Bulgaria The type specimen is provided with a red printed label: "HOLOTYPUS", "Pselaphodes fansipanensis sp. n.", "R. Bekchiev & Zi-Wei Yin, 2019 " .
Length of aedeagus 0.77 mm, median lobe broad and asymmetrical, parameres elongate, endophallus with one elongate sclerite (Fig. 3d, e); the apical part of the median lobe was broken and lost during the preparation of the specimen.

Etymology
The new species is named after Fansipan Summit, the type locality of the new species.

Distribution
North Vietnam: Lao Cai Province.

Taxon discussion
The new species can be readily separated from all other members of the genus by the unique modification of the antennomeres 9-10 and the short, triangular metaventral processes of the male, as well as the shape of the aedeagus.