Genus NiponiusLewis, 1885 is a monotypic genus belonging to subfamily Niponiinae Fowler, 1912. They are known as predators of bark beetles (Ôhara, 1994;Caterino and Vogler, 2002;Khanday et al., 2018). Lewis (1885) firstly erected the genus Niponius as one of genera of family Histeridae. Fowler (1912) separated them from Histeridae as family Niponiidae, however Gardner (1935) regarded them as a subfamily of Histeridae, based on morphology of adults and larvae. A total of 24 species present worldwide, most of them are distributed in Oriental and Palaearctic region, including four Japanese species (Mazur, 2011;Lackner et al., 2015). Only one species, Niponius osorioceps Lewis, is known from Korea (Lee et al., 2012).

Genus GnathoncusJacquelin du Val, 1858 is one of genera belonging to subfamily Saprininae Blanchard, 1845. They are known as inquiline group, especially living in nests of birds and eating larvae of fleas (Kryzhanovskij and Reichardt, 1976;Lackner, 2010). Gnathoncus was firstly classified as a member of saprinine histerids by Marseul (1862) and consistently treated as a genus of Saprininae (Bickhardt, 1910;Reichardt, 1941;Kryzhanovskij and Reichardt, 1976;Vienna, 1980;Ôhara, 1994;Lackner, 2010). This group is mainly distributed in Holarctic region, including three Japanese species (Mazur, 2011;Lackner et al., 2015). Until now, no species have been reported from Korea.

In this study, we recognized two new records of histerid beetles: Niponius impressicollisLewis, 1885 and Gnathoncus nannetensis (Marseul, 1862). We present diagnoses for genera and species, photographs for diagnostic characters.

Materials and Methods

Most specimens examined for this study were collected by flight intercept traps and pitfall traps between 2016 and 2018. All collected samples were preserved in 95% alcohol and made into dried specimens for exact identification. Photographs for each species were taken by a digital camera (EOS-600D, CANON, Japan) through MP-E 65 mm lens. Several taken layers of pictures were stacked by the software (Zerene Stacker 1.04, Zerene Systems, USA). All specimens used in this study are deposited in the insect collection of the College for Agriculture and Life Sciences, Seoul National University (CALS, SNU, Seoul, Korea). Terminology and morphological concepts used in present study mostly follows Ôhara (1994).

Systematic accounts

Family Histeridae Gyllenhal, 1808

Subfamily Niponinae Fowler, 1912

Genus NiponiusLewis, 1885

Niponius Lewis, 1885: 333. Type species: Niponius impressicollis Lewis, 1885: 333.

ArunusSengupta and Pal, 1995: 142. Type species: ArunusmagnusSengupta and Pal, 1995: 144.

Diagnosis.Head: epistomal projection well-developed, stout, carinate at apex with 1-2 subapical carinae; mandible bidentate, with two small teeth in middle; antennae with apical 4-segmented club. Prothorax: pronotum parallel-sided, truncate at anterior margin; procoxal cavities narrowly closed posteriorly; prosternal process broad, with a pair of longitudinal grooves or striae. Pterothorax: elytra truncate at apex, exposing propygidium and pygidium; meso- and metaventrite with broad median groove. Abdomen: propygidium and pygidium foveolate, usually with 2-4 foveae (Lewis, 1885;Fowler, 1912;Gardner, 1935).

Niponius impressicollisLewis, 1885 큰두뿔풍뎅이붙이(신칭) (Fig. 1A-P)

Niponius impressicollisLewis, 1885: 333.

Diagnosis.Body: 4.5-6.6 mm long and 1.2-1.8 mm wide; elongate, cylindrical; mostly black with ferruginous antennae, epistomal projections, tibial apex, and tarsi; surface strongly glossy (Fig. 1A-D). Head: surface (Fig. 1E) rugose with two transverse carinae at epistomal projections, evenly punctate; antennal grooves (Fig. 1F) deeply excavate under eyes; ventral plates with a distinct median groove; antennal scape elongate, almost two-thirds as long as funicle-club segments combined; antennomere VII with several long pubescence near apex; antennomeres VIII-XI (club segments) densely setose apically. Prothorax: pronotum (Fig. E) covered with irregular-sized and scattered punctures, densely pubescent along anterior margin, with a pair of distinct dimples medio-laterally; prosternal lobe transverse, bisinuate at anterior margin with dense pubescence; prosternal keel (Fig. 1F) broad, abruptly widened posterad from apical one-third, broadly rounded at apex. Pterothorax: elytra covered with irregular-sized punctures; marginal epipleural stria short, present on basal one-tenth; marginal elytral stria complete, its apical end attaining elytral apex; dorsal stria I present basal on one-fourth; dorsal striae II-V mostly obsolete; sutural stria present on basal two-thirds with deep and large punctures; meso-metaventral suture complete; metaventrite with a wide median longitudinal groove; lateral metaventral stria strongly carinate, abruptly curved at apical end, not united with posterior margin; lateral disc coarse, covered with large punctures, gradually finer posterad (Fig. 1G). Abdomen: propygidium (Fig. 1H) with four large, round and shallow dimples in a row, sometimes fused in two, interspace covered with irregular-sized punctures; pygidium with a pair of large and round dimples laterobasally, interspace punctate as propygidium; intercoxal disc of abdominal ventrite I with a pair of lateral striae on basal three-fourths. Protibia with two denticles on outer margin near apex (Fig. 1P). Male genitalia shown as Fig. 1 (Fig. 1I-N). Female genitalia shown as Fig. 1 (Fig. 1P).

Specimens examined. 1♀, Gwidun-ri, Inje-eup, Inje-gun, Gangwon-do, 23.v.-04.v.2018, leg. Seung et al., by flight intercept trap; 1♂, ditto, 04-19.vi.2018, leg. Seung et al., by flight intercept trap; 1♂2♀, Yongdae-ri, Buk-myeon, Inje-gun, Gangwon-do, 08-23.v.2018, leg. Seung et al., by flight intercept trap; 5♂7♀, ditto, 23.v.-04.vi.2018, leg. Seung et al., by flight intercept trap; 5♂7♀, ditto, 05-18.vi.2018, leg. Seung et al., by flight intercept trap; 4♂3♀, ditto, 18.vi.-04.vii.2018, leg. Seung et al., by flight intercept trap; 1♂1♀, Osaek-ri, Seo-myeon, Yangyang-gun, Gangwon-do, 08-23.v.2018, leg. Seung et al., by flight intercept trap; 1♀, ditto, 05-19.vi.2018, leg. Seung et al., by flight intercept trap; 2♂1♀, ditto, 19.vi.-05.vii.2018, leg. Seung et al., by flight intercept trap; 1♂, Seorim-ri, Seo-myeon, Yangyang-gun, Gangwon-do, 23.v.-08.vi.2018, leg. Seung et al., by flight intercept trap.

Distribution. Korea (New record), China, Japan, Russia, Taiwan.

Remarks. N. impressicollis can be easily distinguished from N. osorioceps Lewis, 1885 by following characters: body size larger; head with rather short and deep antennal groove, not extending posterior tentorial pit; submentum of head with a deep medio-longitudinal groove; pronotum with a pair of deep foveae medio-laterally. They are thought to be predators of scolytid beetles (Ôhara, 1994).

Subfamily Saprininae Blanchard, 1845

Genus GnathoncusJacquelin du Val, 1858

GnathoncusJacquelin du Val, 1858: 112. Type species: Hister rotundatusKugelann, 1792: 305.

Diagnosis.Head: frons without frontal stria and supraorbital stria; antennae with apical 3-segmented club. Prothorax: pronotum narrowed anterad, weakly emarginate at anterior margin, punctures often forming longitudinal rugae laterally; prosternal keel with striae, strongly convergent anteriorly; lateral prosternal stria shortened. Pterophorax: elytra with two marginal epipleural stria; dorsal elytral stria IV never connected to sutural stria. Abdomen: abdominal ventrite I with lateral stria; male tergite IX divided longitudinally (Jacquelin du Val, 1858;Kryzhanovskij and Reichardt, 1976;Lackner, 2010).

Gnathoncus nannetensis (Marseul, 1862) 애둥근풍뎅이붙이 (신칭) (Fig. 2A-T)

Saprinus nannetensisMarseul, 1862: 499.

Gnathoncus suturalisGanglbauer, 1899: 380.

Gnathoncus urganensisReitter, 1896: 307.

Diagnosis.Body: 2.4-3.7 mm long and 1.1-1.7 mm wide; oval, fairly convex; mostly black with red-brown antennae, elytral apex, tibiae, and tarsi; surface strongly glossy (Fig. 2A-D). Head: frons (Fig. 2E) sparsely covered with round punctures, interspace scattered with finer punctures, becoming larger and coarser posterad; epistomal apex almost straight; labrum broadly rounded at anterior margin. Prothorax: pronotum narrowed anterad, weakly emarginate at anterior margin; surface (Fig. 2E) sparsely and evenly punctate at middle, becoming larger and coarser along posterior margin and lateral regions; marginal pronotal stria complete; prosternum (Fig. 2F) rounded at anterior margin; prosternal keel gradually widened posterad, emarginate at apex, with a distinct excavation near base. Pterothorax: elytra covered with fine punctures on basal two-fifths, fairly largely punctate on apical two-thirds and basal margin of elytra, becoming coarser laterally; marginal epipleural stria complete, internal marginal epipleural stria complete; marginal elytral stria complete, its apical end extending along apical margin of elytron, reaching sutural line, then shortly extending anterad; oblique humeral stria impressed on basal one-third, with densely crossed rugae; dorsal elytral stria I well impressed, nearly complete; dorsal stria II and IV deeply impressed on basal half; dorsal stria III slightly longer than II and IV; dorsal stria V shortly impressed basally, nearly arched; sutural stria usually well impressed on basal one-fifth, more or less variable; mesoventrite (Fig. 2H) bisinuate at anterior margin, coarsely punctate; marginal mesoventral stria complete; meso-metaventral suture accompanied by crenate line; metaventrite sparsely punctate at middle, becoming larger laterally and posteriorly; lateral metaventral stria extending latero-posterad, not united with posterior margin; lateral disc covered with large, irregular-sized punctures. Abdomen: propygidium (Fig. 2G) evenly covered with fine and rounded punctures on basal half, rather larger and coarser posterad; pygidium wholly covered with rounded and regular punctures, slightly finer along margin; intercoxal disc of abdominal ventrite I with a pair of lateral striae, not reaching posterior margin. Protibia deeply emarginate on outer margin near apex (Fig. 2I). Male genitalia shown as Fig. 2 (Fig. 2J-S). Female genitalia shown as Fig. 2 (Fig. 2T).

Specimens examined. 2♂1♀, Myeonggae-ri, Nae-myeon, Hongcheon-gun, Gangwon-do, 06-18.vi.2018, leg. Seung et al., by flight intercept trap; 1♀, ditto, 19.vi.-06.vii.2018, leg. Seung et al., by flight intercept trap; 1♀, Gwidun-ri, Inje-eup, Inje-gun, Gangwon-do, 17.iv.-08.v.2018, leg. Seung et al., by flight intercept trap; 1♂1♀, ditto, 04-19.vi.2018, leg. Seung et al., by flight intercept trap; 2♂, Hangye-ri, Buk-myeon, Inje-gun, Gangwon-do, 06-30.vi.2018, leg. Seung et al., by flight intercept trap; 2♂1♀, Yongdae-ri, Buk-myeon, Inje-gun, Gangwon-do, 08-23.v.2018, leg. Seung et al., by flight intercept trap; 5♂3♀, ditto, 23.v.-04.vi.2018, leg. Seung et al., by flight intercept trap; 1♀, ditto, 05-18.vi.2018, leg. Seung et al., by flight intercept trap and pitfall trap; 1♂1♀, Hoenggye-ri, Daegwallyeong-myeon, Pyeongchang-gun, Gangwon-do, 20.iv.-17.v.2017, leg. Seung et al., by flight intercept trap; 1♂, Nodong-ri, Yongpyeongmyeon, Pyeongchang-gun, Gangwon-do, 24.v.-06.vi.2018, leg. Seung et al., by flight intercept trap; 2♂1♀, ditto, 07-20.vi.2018, leg. Seung et al., by flight intercept trap; 1♂ 3♀, ditto, 20.vi.-06.vii.2018, leg. Seung et al., by flight intercept trap; 1♂, Osaek-ri, Seo-myeon, Yangyang-gun, Gangwon-do, 08-23.v.2018, leg. Seung et al., by flight intercept trap; 2♀, ditto, 19.vi.-05.vii.2018, leg. Seung et al., by flight intercept trap and pitfall trap; 2♂3♀, Beopheung-ri, Mureungbeopheung-ro, Mureungdowon-myeon, Yeongwol-gun, Gangwon-do, 15.v.-05.vi.2016, leg. Seung and Jung, by flight intercept trap.

Distribution. Korea (New record), Japan, nearly whole Palaearctic region.

Remarks.Gnathoncus species are morphologically very similar to each other. G. nannetensis can be distinguished from other relative species by following characters: pygidium covered with rounded punctures; prosternal keel with a distinct excavation near base; protibia deeply emarginate near apex of outer margin; male tergite X truncate at apex. They are observed from various habitats such as cadavers and excrements of animals, nests of birds (Ôhara, 1994;Altunsoy et al., 2017).