Thomson (1858) first proposed the genus name Bessobia based on Homalota monticola Thomson. Since Ganglbauer (1895) treated it as a subgenus of the genus Atheta Thomson, many researchers (Fenyes, 1920;Palm, 1970;Benick and Lohse, 1974;Yosii and Sawada, 1976;Smetana, 2004 etc.) followed this subgeneric assignment.

The Atheta subgenus Bessobia contains 24 species in the Palaearctic region. In East Asia, 12 species and one species were recorded in China and in Japan, respectively (Schülke and Smetana, 2015). They are common in diverse microhabitats such as decaying organism and straw piles.

While working on Korean Athetini, Atheta subgenus Bessobia and the species, A. (B.) occulta (Erichson) is discovered in the Korean Peninsula. The first author compared Korean specimens with syntypes deposited in the Museum für Naturkunde (MNHB), Berlin, Germany to have more reliable identification.

In this paper, we present a redescription, habitus photograph, and illustrations of the diagnostic characters. All specimens are deposited in the Chungnam National University Insect Collection (CNUIC), Daejeon, Korea. Terms used here followed Sawada (1972) but we followed Ashe (1984) in some cases to avoid confusion.

Taxonomic Accounts

Genus AthetaThomson, 1858 우리바수염반날개속

Subgenus BessobiaThomson, 1858 긴바수염반날개아속 (신칭)

BessobiaThomson, 1858: 35 (type species: Homalota monticolaThomson, 1852).

TrichiotaMulsant and Rey, 1873: 180 (type species: Bessobia gibberaMulsant and Rey, 1873 = Bessobia fungivoraThomson, 1867).

Diagnosis. Members of the Atheta subgenus Bessobia can be distinguished from other subgenera of Atheta by the combination of the following characters: infraorbital carina incomplete; antennomere 2 about as long as 3 (Fig. 3B); midline of pronotal pubescence directed posteriorly (Fig. 3C) or anteriorly in basal half to fourth and posteriorly in apical half to fourth; mesoventral process distinctly pointed at apex (Fig. 3F); abdominal tergite II with 2 macrosetae on each side of midline, III with anterior macrosetae; VIII with about 6 macrosetae on each side of midline in most (Figs. 4A and C) and longitudinal ridges along lateral margins (Fenyes, 1920;Benick and Lohse, 1974;Yosii and Sawada, 1976).

Distribution. Korea, China, India, Japan, Nepal, Mongolia, Russia, Europe, North Africa and Nearctic region.

Atheta (Bessobia) occulta (Erichson, 1837) 긴바수염반날개 (신칭)

(Figs. 1, 2A~F, 3A~H, 4A~H)

Aleochara foveataStephens, 1832: 111.

Aleochara assimillisStephens, 1832: 117.

Homalota occultaErichson, 1837: 317.

Bessobia nebulosaMulsant and Rey, 1873: 180.

Bessobia diversipesMulsant and Rey, 1875: 135.

Atheta (Bessobia) occulta: Ganglbauer, 1895: 202; Fenyes, 1920: 216; Palm, 1970: 246; Benick and Lohse, 1974: 149; Yosii and Sawada, 1976: 80; Smetana, 2004: 377; Schülke and Smetana, 2015: 524.

Atheta erichsoniBernhauer, 1907: 397.

Redescription. Body length 3.0-3.8 mm, parallel-sided; surface glossy, densely pubescent; dark brown to black; head, pronotum and abdomen almost black; elytra slightly paler; legs brown. Head. Subquadrate (Fig. 3A), approximately 1.1 times as wide as long, slightly narrower than pronotum; eyes about 1.3 times longer than temples; behind eyes convex; gular sutures moderately separated. Antennomere 4 about as long as wide, 5-10 subquadrate to slightly transverse, 11 longer than wide (Fig. 3B). Mouthparts. Labrum (Fig. 2A) with ε-sensillum and 9 macrosetae on each side of midline; epipharynx (Fig. 2B) with α-sensillum long and setaceous, more than 2.0 times as long as ε-sensillum; β- and γ-sensilla short. Mandibles (Figs. 2C and D) asymmetrical, about 1.5-1.6 times as long as basal width; right one (Fig. 2C) with small internal tooth. Galea and lacinia of maxilla (Fig. 2E) long and slender; palpomere 1 smallest, 2 about 2.7-2.9 times longer than wide, 3 slightly longer than 2, about 2.6-2.8 times as long as wide, 4 digitiform. Labium (Fig. 2F) with ligula long and slender, divided into 2 lobes in basal half; prementum with two medial setae moderately narrow separated; two basal pores close together, about 1.0 times width of basal pore; several medial pseudopores, few lateral pseudopores, 1 setal pore and 2 real pores present on each side of midline; labial palpus elongate, with many setulae; palpomere 1 largest, about 1.4-1.6 times longer than wide, with γ-setula close to b-seta, 2 shortest, about 1.4-1.6 times longer than wide, 3 subparallel-sided and about as long as 1, about 3.0-3.5 times longer than wide. Mentum as in Fig. 2F. Thorax. Pronotum (Fig. 3C) slightly transverse, approximately 1.2 times as wide as long. Prosternum as in Fig. 3D. Metanotal scutum (Fig. 3E) with 1 long seta and about 5-8 short setae on each side of midline. Mesoventral process (Fig. 3F) slightly longer than isthmus and metaventral process combined; length ratio of mesoventral process, isthmus and metaventral process 17:10:3. Elytra slightly longer and wider than pronotum; elytron (Fig. 3H) approximately 1.7 times as long as wide, pubescence directed posteriorly and postero-laterally; postero-lateral margin almost straight; flabellum (Fig. 3E) composed of about 6-9 long setose lobes. Legs. with dense pubescence and macrosetae; meso- and metatibiae with different length of two spurs at apex; length ratio of tarsomeres 31:34:40:94 (protarsus); 36: 42:45:47:97 (mesotarsus); 53:54:55:53:114 (metatarsus); one empodial seta present, shorter than claw. Abdomen. Macrochaetal arrangement of tergites II-VI 02-13-23-23-23; tergites III-VI impressed in basal region; posterior margin of male tergite VIII (Fig. 4A) with a broad process almost truncate at apex, imbricate microsculpture present; male sternite VIII (Fig. 4B) with about 10-12 macrosetae on each side of midline; female tergite VIII (Fig. 4C) with about 5 macrosetae on each side of midline; female sternite VIII (Fig. 4D) with long and short marginal setae, minute setae present in median region. Aedeagus. Median lobe (Figs. 4E and F) ovate, apical process convergent in ventral aspect; apical process elongate and slightly bent in lateral aspect. Apical lobe of paramerites (Fig. 4G) slightly elongate and subparallel-sided, blunt at apex. Spermatheca. Bursa elongate, with large umbilicus; duct slender and transversely contorted, deflected at apex (Fig. 4H).

Type material. Syntypes, 6 exx., labeled as follows: ‘5352, occulta Er. Berol. Er.’.

Material examined. SOUTH KOREA:Chungbuk Prov.: 1 ex., Yeongdong-gun, Sangchon-myeon, Mulhan-ri, Mt. Minjujisan, N36˚03'35.22" E127˚52'31.26", 518 m, 13 v 2011, JG Lee, TK Kim, SG Lee, decaying persimmon. Chungnam Prov.: 9 exx., Daejeon-si, Yuseong-gu, Ansan-dong, N36°24′43.9″ E127°17′25.2″, 13 xii 2011, YH Kim, SG Lee, straw piles. Gangwon Prov.: 1 ex., Pyeongchang-gun, Mt. Odaesan, Sangwonsa, 18 v 2002, SJ Park, SW Shin. Gyeonggi Prov.: 2 exx. (one on slide), Namyangju-si, Hwado-eup, Mt. Cheonmasan, 21 v 1984 Ys Kim; 2 exx., Seoul-si, Mt. Cheonggyesan, 15 iv 1989, KJ Ahn; 1 ex., Seoul-si, Gangnam-gu, 20 iv 1985, YS Kim; 1 ex., Seoul-si, Dobong-gu, Taeneung, 16 iv 1988, YS Kim. Gyeongnam Prov.: 9 exx. (one on slide), Jinju-si, Gajwa-dong, Gyeongsang univ., 9 iii 2003, CS Lim, bait trap; 1 ex. (on slide), same data as former except for ‘8 iii 2003’; 2 exx. (on slide), same data as former except for ‘12 iii 2003’. Jeju Prov.: Seogwipo-si, 18 ii 1986, YS Kim.

Distribution. Korea (South), China (Beijing), Japan, Russia (Siberia, North European Territory), Turkey, Europe and North Africa.

Remarks. This species is widely distributed in the Palaearctic region and is recorded here for the first time in Korea. As Yosii and Sawada (1976) pointed out, the number of macrosetae on tergite VIII is variable of ranging 5-7 on each side of midline in this species. We examined four slide-mounted specimens.