A male of the very rare and phylogenetically puzzling species, Quelaestrygon puetzi Smetana, 1999, is described for the first time based on a single specimen from Sichuan Province, China. High quality color images and line drawings of the male external and genitalic traits are provided.

Morphology, rove beetle, taxonomy

The monotypic genus Quelaestrygon Smetana, 1999 (Staphylinidae, Staphylininae, Staphylinini) was established based on two female specimens of Quelaestrygon puetzi Smetana, 1999 collected from the mountain areas in Sichuan, China.

Initially, this distinctive genus was assigned to the subtribe Quediina mostly due to its overall similarity to the other members of the subtribe. Later, a series of phylogenetic studies of Staphylinini were successively conducted by various authors (e.g., Solodovnikov 2006; Solodovnikov and Schomann 2009; Chatzimanolis et al. 2010; Brunke and Solodovnikov 2013; Brunke et al. 2016; Żyła and Solodovnikov 2019; Tihelka et al. 2020). As a result, the subtribe Quediina was confirmed to be highly polyphyletic and redefined as a more restricted group, while many genera were moved out from Quediina sensu Brunke et al. (2016). The systematic position of some of them, including Quelaestrygon Smetana, unfortunately, is still unclear (Brunke et al. 2016).

This peculiar genus is mainly characterized by its large size and the long appendages (Fig. 2A), the simultaneous presence of the postmandibular and infraorbital ridges on the head (Fig. 1D), the distinct basolateral mandibular ridge, removed from the lateral mandibular margin and bordered by a deep and very wide depression (Fig. 1A), the first four antennal segments devoid of dense appressed pubescence (Fig. 1E), the absence of dorsal rows of punctures on the pronotum (Fig. 1B), and the surface sculpture of the elytra with fine leather-like rugulae and scratch-like short lines, lacking the usual punctation and pubescence (Fig. 1C) (Smetana 1999).

Examination of rove beetle specimens collected from Sichuan Province, China revealed a male of this rare species. The aim of this study was to describe the male of Q. puetzi Smetana, in the hope that the new information provided could help with future resolution of this taxonomically uncertain genus.

The male specimen was relaxed in warm water (60 °C) for 5–8 hours for dissection of the abdominal segments VIII–X and the genitalia. After examination, the dissected body parts were glued back to the mounting card for future study. Observation, dissection and measurements were performed using a stereo microscope (Zeiss SteREO Discovery V20). Images of the adult and genitalia were captured with an AxioCam MRc 5 camera attached to a Zeiss Axio ZoomV16 Fluorescence Stereo Zoom Microscope, and photomontage was performed in Zen 2012 (blue edition) imaging software. Inkscape V0.91 was used to make the line drawings. The abdominal tergites and sternites were entirely flattened for the line drawings to make the illustrations more comparable among species.

The specimen examined was deposited in the Institute of Zoology, Chinese Academy of Sciences (IZ-CAS).

Morphological terminology followed Smetana (1999), Smetana and Davies (2000).

The following abbreviations are used in the text:

BL body length (from apex of clypeus to apex of abdominal tergite VIII);

BW body width (maximal body width, usually equal to EW);

HL head length (from base of clypeus to neck constriction);

HW head width (maximal head width, including eyes);

PL pronotal length (along midline of pronotum);

PW pronotal width (maximal pronotal width);

EL elytral length (maximal elytral length);

EW elytral width (maximal elytral width);

ESL elytral suture length (from apex of scutellum to apex of elytral suture);

AW abdominal width (maximal width of abdomen);

HEL (head) eye length;

HTL (head) temporal length.

We want to thank the editors and the reviewers for reviewing this manuscript and giving a lot of constructive suggestions, and also, we are very grateful to Dr Chengbin Wang (MYNU) for the field investigation and the collection of the material of this species. This project was supported by the National Natural Science Foundation of China (No. 31760629), Guizhou Provincial Department of Education Youth Science and Technology Talent Growth Project (黔教合KY字[2017]175) and the Natural Science Foundation of Hebei Province (C2019408016).