Revision of the genus Ptomaphagus Hellwig (Coleoptera, Leiodidae, Cholevinae) from the Russian Far East and the Korean Peninsula

Abstract The conundrum of Ptomaphagus (s. str.) sibiricus Jeannel, 1934 (Coleoptera, Leiodidae, Cholevinae, Ptomaphagini) is solved, and it is redescribed and newly recorded in South Korea. A new species is also described from the Russian Far East: Ptomaphagus (s. str.) hayashii sp. n. Relevant morphological characters of the concerned species are illustrated with colour plates, and their known distributions are mapped.


Introduction
Ptomaphagus Hellwig, 1795 is the most speciose genus (including 137 known species worldwide) in the tribe Ptomaphagini (Coleoptera, Leiodidae, Cholevinae). However, the nominotypical subgenus, which is limited to the Palaearctic and north Oriental regions has only 29 species (Perreau 2000, Nishikawa 2011, Wang et al. 2016a, 2016b. In the fauna of the Russian Far East, only one species in the subgenus Ptomaphagus s. str. had been recorded before this study, namely P. (s. str.) sibiricus Jeannel, 1934. However, when we examined specimens previously identified as Ptomaphagus (s. str.) sibiricus from various collections, we discovered that three species were identified under this name by different authors. One of them with conspicuous differences from Japan was already described in a previous paper: P. (s. str.) piccoloi Wang, Růžička, Nishikawa, Perreau & Hayashi, 2016(Wang et al. 2016a. In this paper, we solve the conundrum of P. (s. str.) sibiricus, and redescribe it and report it for the first time in South Korea. The third species from the Russian Far East is also new, and is described and illustrated here: P. (s. str.) hayashii sp. n. Relevant morphological characters of examined species of Ptomaphagus are illustrated with colour plates, and their known distributions are mapped.

Material and methods
Specimens were relaxed and softened in a hot saturated solution of potassium hydroxide for 4 minutes (for mounted dry specimens) or 8 minutes (for alcohol-preserved specimens), and then transferred to distilled water to rinse the residual potassium hydroxide off and stop any further bleaching. The softened specimens were moved into glycerin and dissected there to observe morphological details. After examination, the body parts were mounted on a glass slip with Euparal Mounting Medium for future studies. Habitus photographs were taken using a Canon macro photo lens MP-E 65mm on a Canon 550D. Observations, photographs and measurements of morphological details were performed using an Olympus BX53 microscope with an Olympus DP73. The final deep focus images were created with Zerene Stacker 1.04 stacking software. Adobe Photoshop CS6 was used for post processing. Exact label data are cited for specimens examined. Authors' remarks and addenda are placed in square brackets, separate label lines are indicated by a slash (/), and separate labels by a double slash (//). Measurements are averaged over 5 specimens.
The material examined for this study is deposited in the following collections and museums: The following abbreviations are used for the measurements in millimetres (mm):

EBL
(extended body length): summation of HL, PL, ELL and length of exposed scutellum, preventing the error introduced by exposed or retracted head.      Habitus (Fig. 1B) elongated oval, regularly convex and sublustrous. Well pigmented: mostly blackish brown; mouthparts, antennae (apical half of ultimate antennomere yellowish) and tarsi reddish brown. Dorsum continuously clothed with fine, recumbent, yellowish pubescence. Insertions of pubescence on dorsal surfaces of pronotum, elytra and femora aligned along transverse striolations; interspace between two striolations glabrous.
Abdominal ventrite VIII (Fig. 2I) round at posterior edge and with an inconspicuous median notch. Spiculum gastrale (Fig. 2J) of genital segment with about 1/5 of length protruding beyond anterior edge of epipleurite IX. Aedeagus (Fig. 3A) long and slender, with median lobe gradually narrowing towards a lanceolate apex and terminated to a widely rounded knob in dorsal view; opening of genital orifice situated on dorsal surface, deeply cut inwards on preapical left margin of median lobe. Ventral surface of the apex of the median lobe (Fig. 3C) inserted with 5 ventrally oriented setae on both sides; parameres narrow, reaching about apical 1/5 of median lobe, each apex ( Fig. 3D) with 2 lateral setae and 1 apical seta distinctly shorter. In lateral view (Fig. 3B), median lobe regularly bent ventrad and gradually tapering to a flat apex. Endophallus with stylus quite slender, a subelliptical nodule in middle region, a cheliform complex just below base of stylus, and a circular complex in the basal region.
Female. Similar to male in general appearance (Fig. 1C), including elytral apices (Fig. 2H), but distinguished by the following characteristics: protarsi (Fig. 2D) (Figs 1B, C). However, their aedeagi provide critical characters to distinguish the two species: in P. (s. str.) hayashii sp. n., the aedeagus is much larger and more slender (Fig. 3A), the right apicoventral piece of the median lobe is slenderly lanceolate (Fig. 3C), the apical half of median lobe much flatter in lateral view (Fig. 3B); while in P. (s. str.) sibiricus, the aedeagus is stouter (Fig. 5A), the right apicoventral piece of median lobe is much wider and subpentagonal (Fig. 5C), the apical half of the median lobe thicker in lateral view (Fig. 5B).
Furthermore, based on specimens examined, P. (s. str.) sibiricus seems to be much more widely distributed, extending southward to South Korea; while P. (s. str.) hayashii sp. n. is presently known only in the Russian Far East.
Etymology. The specific epithet is dedicated to Mr. Yasuhiko Hayashi (Kawanishi, Japan), a famous independent taxonomist on Staphylinoidea, for his continual generous help to our study.
Abdominal ventrite VIII (Fig. 4I) rounded and with an inconspicuous median notch at posterior edge. Spiculum gastrale (Fig. 4J) of genital segment with about 1/5 of length protruding beyond anterior edge of epipleurite IX. Aedeagus (Fig. 5A) long, slender but relatively strong, with median lobe gradually narrowing towards a wide subpentagonal apex and terminated to a widely rounded knob in dorsal view; opening of genital orifice situated on dorsal surface, deeply cut inwards on preapical left margin of median lobe. Ventral surface of the apex of the median lobe (Fig. 5C) inserted with 6 ventrally oriented setae on the left side and 5 ventrally oriented setae on the rigth side; parameres narrow, reaching about apical 1/6 of median lobe, each apex ( Fig. 5D) with 2 lateral setae and 1 apical seta distinctly shorter. In lateral view (Fig. 5B), median lobe thick, regularly bent ventrad, and gradually tapering to a thin apex. Endophallus with stylus quite slender, a cheliform complex just below base of stylus, and a circular complex in the basal region.