Revision of Korean species of the genus Batriscenellus Jeannel (Staphylinidae, Pselaphinae, Batrisitae) with description of one new species

Abstract The genus Batriscenellus Jeannel, 1958 (type species: Batrisus fragilis Sharp) includes 35 species and is known from South Korea, China, Japan, Russia, and India. Three species, B. vicarius, B. auritus, and B. orientalis have been documented from the Korean Peninsula. One additional species, Batriscenellus koreanussp. nov., is described as new. Redescriptions of the Korean species, a species key, illustration of habitus, and diagnostic characters are provided.


Introduction
The genus Batriscenellus Jeannel, 1958 was described based on Batrisus fragilis Sharp from Kioto, Japan. It includes 35 species and is known from South Korea, China, Japan, Russia, and India (Yin 2020). Three species, B. vicarius Löbl, 1973, B. orientalis (Löbl, 1973), and B. auritus (Löbl, 1974) are known from the Korean Peninsula. The first Korean species of the genus, Batriscenellus japonicus vicarius Löbl, 1973 was described from the northern part of the Korean Peninsula. It was subsequently raised to the species level by Nomura and Lee (1992). Löbl (1973Löbl ( , 1974 described two additional species, Batrisiella aurita and Batrisiella orientalis, also from the northern part of the Korean Peninsula, and they were transferred to Batriscenellus by Yin et al. (2011) and Nomura (1991), respectively.
During a revisionary study of the Korean Batriscenellus species, we documented four species, the previously known three species and one new species. The present paper presents the first revisionary study of Korean species of Batriscenellus, and describes the new species. This new species brings the number of Batriscenellus species from the Korean Peninsula to four.

Materials and methods
Twenty-two specimens were examined. They are deposited in the following collections: At least one specimen of each species was dissected to study male genitalia and other detailed characters. Terminology and nomenclature using descriptions follow Chandler (2001). Numbering of abdominal sclerites indicates a morphological segment. Specimen label data for the holotypes is transcribed verbatim. Data for the other specimens are standardized for consistency. Application of the terms 'dorsal' and 'lateral' to the male genitalia including the right and left apical lobe and the paramere refer to the orientation in the illustrations. The specimens were observed using a Leica M80 and MD 1000 LED optical microscope and images generated using Leica Las version 4.12 and Zerene Stacker. The map of South Korea is based on an image from Sim-pleMappr (Shorthouse 2010) that was subsequently modified to add locality marks.
Key to Korean species of the genus Batriscenellus Jeannel 1 Abdominal tergite IV or VI without depression; phallobase of male genitalia without apophysis (Fig. 8)  Diagnosis. Members of this genus are easily separated from other genera of Batrisitae by the following combination of characters: head triangular with the transverse sulcus dorsally at mid-level of head and vertexal foveae; antennomere 1 subquadrate with dense trichomes (Figs 1C, 3B, 5B, 7B), antennomeres 9-11 clubbed; pronotum with median antebasal fovea, lateral antebasal foveae, inner basolateral foveae and outer basolateral foveae, disc with median and lateral longitudinal sulci; elytra with two basal foveae; mesotibia with spine on distal margin (  Diagnosis. This species can be distinguished from the other Batriscenellus species by the following combination of characters: antennomere 8 subquadrate and smallest (Fig. 1C), abdominal tergite V with a pair of median setiferous patches, VI with deep mediobasal sulcus (Fig. 1D), abdominal ventrite VIII with depressionand pair of dense setiferous patches (Fig. 1E), phallobase of male genitalia widely expanded, apical lobe of male genitalia curved to right in lateral view (Fig. 2C, D), paramere forked into two branches in lateral view, major branch curved to right (Fig. 2C, D).
Distribution. South Korea ( Fig. 9: square) Etymology. This species is named for Korea, where this species was collected.
Habitat. The two specimens of this species were collected by sifting soil litter of a riverside grassland. Löbl, 1973 Figs 3, 4 Batriscenellus japonicus vicarius Löbl, 1973: 322. Nomura 1991.    Diagnosis. This species can be distinguished from the other Batriscenellus species by the following combination of characters: antennomeres 2-8 rectangular (Fig. 3B); abdominal tergite V with pair of basolateral setiferous patches, VI with deep sulcus ( Fig. 3C: arrow); abdominal ventrites IV-VII with pair of long setae at middle (Fig. 3D), VIII with carina and pair of dense medial setiferous patches (Fig. 3D: arrow); left side of phallobase of male genitalia widely expanded in dorsal view (Fig. 4A, B: arrow); paramere of male genitalia curved to left in dorsal view (Fig. 4A, B).
Habitat. Specimens of this species were collected by sifting soil or leaf litter.
Comments. The basal bulb of the male genitalia are broken in Figure 6D. See Löbl (1974: 93) for other examples of the aedeagus.

Habitat.
A single specimen of this species was collected near a stream.
Habitat. Most specimens of this species were collected by sifting leaf litter or dead wood debris. One specimen was captured by a light trap.