A taxonomic review of Korean species of the Atheta Thomson subgenus Microdota Mulsant & Rey, with descriptions of two new species (Coleoptera, Staphylinidae, Aleocharinae)

Abstract A taxonomic review of the Atheta Thomson subgenus Microdota Mulsant & Rey in Korea is presented. The subgenus is represented in Korea by 15 species including two new species, Atheta (Microdota) jangtaesanensis Lee & Ahn, sp. n. and Atheta (Microdota) pasniki Lee & Ahn, sp. n. Four species [Atheta (Microdota) kawachiensis Cameron, Atheta (Microdota) muris Sawada, Atheta (Microdota) spiniventris Bernhauer, and Atheta (Microdota) spinula (Sawada)] are new to the Korean Peninsula and two [Atheta (Microdota) formicetorum Bernhauer and Atheta (Microdota) subcrenulata Bernhauer] to South Korea. Two other species [Atheta (Microdota) kobensis Cameron and Atheta (Microdota) scrobicollis (Kraatz)] previously recorded in North Korea had been identified incorrectly. A key, descriptions, habitus photographs and illustrations of the diagnostic features are provided. Species distributions and diversity in East Asia are discussed.

Distribution. Korea (South, North) and Japan.
Remarks. This species is identified for the first time in South Korea. Most specimens were found on mushrooms in forest. Description. Length 1.6-1.8 mm. Body (Fig. 3) slender and parallel-sided, more or less flattened; surface distinctly glossy and densely pubescent, with fine microsculpture. Body usually reddish brown; head and abdomen slightly darker than other parts; antennae and legs paler. Head. Subquadrate, about as wide as long, widest across eyes, slightly narrower than pronotum; eyes small and slightly prominent, about 0.6-0.7 times longer than tempora; infraorbital carina incomplete; gular sutures moderately separated, dilated apically. Antennae dilated apically; antennomeres 1-3 elongate, 1 longest, 4-10 distinctly transverse, 11 longer than wide, about as long as preceding two combined. Thorax. Pronotum transverse, approximately 1.3 times wider than long, widest at apical third; pubescence directed posteriorly in midline. Elytra slightly transverse, slightly wider than pronotum, elytron approximately 1.5 times longer than wide, pubescence directed posteriorly and postero-laterally; postero-lateral margin slightly sinuate; hind wings fully developed. Legs. Slender and long, with dense pubescence and setae; tibiae with two spurs at apex; mesoand metatarsomeres 1-4 subequal in length. Abdomen. Parallel-sided, widest at middle; surface distinctly glossy and densely pubescent; male tergite VIII with 4 macrosetae on each side of midline, posterior margin subtruncate; male sternite VIII with 7 macrosetae on each side of midline, posterior margin rounded. Genitalia. Median lobe (Paśnik 2001: Figs 30-31) oval; apical process abruptly convergent at apex in ventral aspect.
Remarks. This species was recorded by Paśnik (2001) in North Korea and a dissected specimen was unavailable. Accordingly, we could not describe the mouthparts and aedeagus in detail.
Etymology. Named after the type locality Mt. Jangtaesan, where all of specimens were collected.
Remarks. All specimens were collected by sifting leaf litter in Gangwon province.

Atheta (Microdota) pasniki
Distribution. Korea (South). Remarks. This species is similar to A. (M.) nakanei, but can be distinguished by shape and structure of internal sac of aedeagus. They were usually collected near streams or in moist regions of forest of Gangwon province by sifting litter.

Atheta (Microdota) silvatica
Description. Length about 1.5-2.0 mm. Body (Fig. 11) slender and parallel-sided, more or less flattened; surface distinctly glossy and densely pubescent, with fine microsculpture. Body usually reddish brown; head slightly darker than pronotum and elytra; legs yellowish brown. Head. Subquadrate, approximately 1.0-1.1 times wider than long, widest across eyes, slightly narrower than pronotum; eyes small, about 0.8 times longer than tempora; infraorbital carina complete; gular sutures moderately separated, diverged basally. Antennae dilated apically, longer than head and pronotum combined; antennomeres 1-3 elongate, 1 longest, 4 about as long as wide, 5-10 distinctly transverse, 11 longer than wide, about as long as preceding two combined. Thorax. Pronotum transverse, approximately 1.3-1.4 times wider than long, widest at apical third; pubescence directed anteriorly in midline. Elytra slightly transverse, slightly wider than pronotum, elytron approximately 1.7-1.8 times longer than wide, pubescence directed posteriorly and postero-laterally; postero-lateral margin almost straight; hind wings fully developed. Legs. Slender and long, with dense pubescence and setae; tibiae with two spurs at apex; meso-and metatarsomeres 1-4 subequal in length. Abdomen. Parallel-sided, widest at middle; surface distinctly glossy and densely pubescent; male tergite VIII with 4 macrosetae on each side of midline, posterior margin emarginated at middle; male sternite VIII with 8 macrosetae on each side of midline, posterior margin broadly rounded. Genitalia. Median lobe oval, apical process slightly decurved at apex in lateral aspect.
Distribution. Korea (North) and Japan.
Remarks. This species was recorded by Paśnik (2001) in North Korea and a dissected specimen was unavailable. Accordingly, we could not describe the mouthparts and aedeagus in detail. This species is distinguished from similar species by the characters provided in Sawada (1974). Fig. 12 Atheta (Microdota) sogamensis Paśnik, 2001: 210;Smetana 2004: 388 (as valid species).
Description. Length about 2.0 mm. Body (Fig. 12) slender and parallel-sided, more or less flattened; surface distinctly glossy and densely pubescent, with fine microsculpture. Body usually reddish brown to dark brown; head almost black; elytra paler than other parts; legs yellowish brown. Head. Slightly transverse, approximately 1.1-1.2 times wider than long, widest across eyes, slightly narrower than pronotum; eyes large and prominent, about 1.5 times longer than tempora; infraorbital carina incomplete; gular sutures moderately separated, diverged basally. Antennae dilated apically, longer than head and pronotum combined; antennomeres 1-3 elongate, 1 longest, 4 about as long as wide, 5-10 distinctly transverse, 11 longer than wide, about as long as preceding two combined. Thorax. Pronotum transverse, approximately 1.3-1.4 times wider than long, widest at apical third; pubescence directed anteriorly in midline. Elytra slightly transverse, slightly wider than pronotum, elytron approximately 1.7 times longer than wide, pubescence directed posteriorly and postero-laterally; posterolateral margin almost straight; hind wings fully developed. Legs. Slender and long, with dense pubescence and setae; tibiae with two spurs at apex; meso-and metatarsomeres 1-4 subequal in length. Abdomen. Parallel-sided, widest at middle; surface distinctly glossy and densely pubescent; male tergite VIII with 4 macrosetae on each side of midline, posterior margin broadly rounded; male sternite VIII with 7 macrosetae on each side of midline, posterior margin rounded. Genitalia. Median lobe (Paśnik 2001: figs 28-29) elongated oval, apical process convergent at apex in ventral aspect.
Distribution. Korea (South) and Japan.
Remarks. This species is very similar to Atheta (Microdota) amicula, but can be distinguished by the internal sac of median lobe and spermatheca.
Remarks. The North Korean record of the species by Paśnik (2001) is a misidentification of other Atheta (Microdota) species. This species is unlikely to be found in Korea as its distribution has shown that it occurs in southern Europe and subtropical regions. This species differs from a syntype of A. (M.) scrobicollis by several diagnostic characters although we were not able to identify it due to a paucity of specimen. Cameron, 1933 Material examined. Syntype, 3 exx., labeled as in Figs 89-91. NORTH KOREA: 2 exx., Korea 1981 Kymgangsan A. Szeptycki [North Korea, Gangwon Prov., Mt. seem not to be mycetophagous. Atheta (M.) subcrenulata was usually found in decaying vegetables and straw piles. No habitat preference of North Korean species is available.

Atheta (Microdota) kobensis
Since the first record of Korean Microdota species by Bernhauer (1923), 11 species were recorded in North Korea (Paśnik 2001). Two species are removed from the Korean fauna and six species are added to the Korean fauna in this study. Consequently, the number of Microdota species known to occur in the Korean Peninsula increases from 11 to 15. Five species [Atheta (Microdota)  Compared with other north temperate regions, such as Czech Republic (17 species), Great Britain (16 species), Spain (13 species), and Turkey (11 species), the diversity of Korean Microdota is close to that of the regions (Smetana 2004). However, it appears a bit lower than that of adjacent Japan (20 species). Although the Japanese archipelago is an area of relatively high endemism for Microdota, this study decreases the number of species considered endemic to this area from 14 (70%) to 11 (55%) (Smetana 2004). Without doubt, further collecting efforts and the study of Korean species will increase opportunity to discover additional Atheta (Microdota) species.