Journal 
The genus OdontalgusRaffray, 1877 currently comprises 49 species and three subspecies (Yin et al., 2016). Most species are distributed in the Africa region (Arai and Nomura, 2003;Yin et al., 2016). In East Asia, three species have been recorded: O. coreanusLöbl, 1973 from North Korea and Japan, O. masaoiArai and Nomura, 2003 from Japan, and O. dongbaiensis Yin and Zhao, 2016 from China. In Korea, a species of Odontalgus was first recorded from North Korea by Löbl (1973), and since then, no additional species have been reported.
Herein, we report O. masaoi for the first time from Korea. In addition, we provide habitus, diagnostic character images, a distribution map, and an identification key to Korean species of Odontalgus.
Material and Methods
A total of 12 specimens of this species were examined (11 type specimens and one non-type specimen). The type specimens and the non-type specimen were observed using an Olympus SZX7 and a Leica S8APO stereomicroscope, respectively. Images of the habitus and diagnostic characters were taken using a Sony ILCE-7RM3 mirrorless camera equipped with Mitutoyo M Plan Apo 10X/20X objective lenses. The aedeagus of the non-type was observed after removing internal tissues using 10% KOH and preserved in glycerol in 0.2 ml microtubes. The resulting image stacks were processed with Zerene Stacker v. 1.04. The distribution map was created using SimpleMappr (Shorthouse, 2010), and all images were edited in Adobe Photoshop 2025. Terminology follows Chandler (2001). Holotype labels were transcribed verbatim. In description of labels, single slash (/) and double slashes (//) indicate ‘line break’ and ‘label break’, respectively. The labels for the other specimens were standardized for clarity.
All specimens examined in this study were deposited in the following collections (institutional codes in parenthetically): CBNUIC, Chungbuk National University Insect Collection, Cheongju, South Korea; NSMT, National Museum of Nature and Science, Tsukuba, Japan.
Taxonomic Accounts
Family Staphylinidae Latreille, 1802 반날개과
Subfamily Pselaphinae Latreille, 1802 개미사돈아과
Supertribe Pselaphitae Latreille, 1802 개미사돈상족
Tribe Odontalgini Jeannel, 1949 고려개미사돈족(신칭)
Genus Odontalgus Raffray, 1877 고려개미사돈속
OdontalgusRaffray, 1877. Type species Odontalgus tuberculatusRaffray, 1877: 287.
= HerminiellaBlattný, 1925: 211. Type species Ctenistes costulatusMotschulsky, 1851 (synonymized by Besuchet, 1986).
Distribution. Afrotropical; Oriental: Myanmar, Indonesia, Vietnam, India; Palearctic: China, Japan, North Korea, South Korea.
Key to the Odontalgus species in Korea
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1. Antennae relatively short, antennomeres 9–10 quadrate (Fig. 2C; fig. 2 in Arai and Nomura, 2003) in male; median lobe of male genitalia sharply extended laterally (Fig. 2G; figs. 6–7 in Arai and Nomura, 2003) ············ ····································································· O. masaoi
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- Antennae relatively long, antennomeres 9–10 rectangular (fig. 4 in Arai and Nomura 2003) in male; median lobe of male genitalia not extended laterally (abb. 26 in Löbl, 1973) ································································· O. coreanus
Odontalgus masaoiArai and Nomura, 2003 닮은고려개미 사돈(신칭)
Odontalgus masaoiArai and Nomura, 2003: 194. Type locality: Saitama Pref.
Odontalgus masaoi: Shibata et al. 2013: 96; Schülke and Smetana, 2015: 441; Nomura and Kamezawa, 2016: 23.
Male Diagnosis. Genae with dense squamous setae, Vshaped (Fig. 2E). Antennomeres 9–10 quadrate, 10 slightly smaller than 9; 11 approximately twice longer than 10 (Fig. 2C). Median lobe of male genitalia apicoventral portion slightly elongated, apical margin somewhat rounded, protruded ventrally; middle of median lobe protruded ventrally. Parameres short; with two short setae on apex. Endophallus elongated; apical portion extended laterally; apicodorsal portion slightly wrapped (Fig. 2G–I).
Male redescription. Body 1.3–1.5 mm (Figs. 1A, 2A); forebody 0.9–1.0 mm. Reddish-brown. Body densely covered with thick white pubescence.
Head. Head triangular; with setose dorsal tentorial pits and frontal fovea; with small tubercles before frontal fovea (Fig. 2B). Vertex convex (Fig. 2E). Frons slightly concave (Fig. 2E). Temples reduced (Fig. 2E). Genae covered with dense squamous setae, V-shaped (Fig. 2E). Eyes large and convex; slightly protruded laterally on posterior margin; with several setae on protruded area (Fig. 2B, E). Gula with a pair of ventral tentorial pits. Maxillary palpomere 1 small; 2 gradually widened distally; 3 small and globular; 4 elongated and clavated, with small spine apically (Fig. 2E, F). Antennae composed of 11-segments; antennomere 1 subrectangular; 2–7 subquadrate; 8 distinctly wider than long; 9–10 quadrate, 10 slightly smaller than 9; 11 approximately twice longer than 10 (Fig. 2C).
Thorax. Pronotum trapeziod; with two pairs of pits before anterior margin, around weakly impressed; with squamously setose median antebasal fovea and lateral antebsal foveae (Fig. 2B). Prosternum with lateral procoxal foveae. Mesoventrite with lateral mesoventral foveae and median mesoventral foveae. Metaventrite with lateral mesocoxal foveae and median metaventral foveae; with transverse carina on middle; medioposterior area strongly impressed.
Elytra. Elytra wider and longer than pronotum; with short setae along posterior margin (Figs. 1A, B, 2A). Each elytron with two setose basal elytral foveae (Fig. 2B); with sutural stria; with four discal striae, extended from fovea to posterior margin (Figs. 1A, B, 2A).
Abdomen. As wide as elytra. Visible tergite 1 with transverse impression before anterior margin; with basolateral foveae. Ventrite 2 with transverse impression before anterior margin; with basolateral foveae; weakly impressed on middle. Ventrites 3–5 weakly impressed on middle.
Legs. Moderately long and slender.
Hindwing. Developed.
Male genitalia. Asymmetric. Median lobe basal portion rounded; with small basal foramen; with large globular dorsal diaphragm; apicoventral portion slightly elongated, apical margin somewhat rounded, protruded ventrally; middle of median lobe protruded ventrally. Endophallus elongated; apical portion extended laterally; apicodorsal portion slightly wrapped (Fig. 2G–I). Paramere short; each with two short setae on apex. More detail description refer to Arai and Nomura (2003).
Type material. Holotype. ♂ (NSMT), OHKURA (Tokigawa-riv. / Ranzan town / Saitama Pref. / 26-X II-1999 / Shiho ARAI leg. // ♂ // HOLOTYPE / Odontalgus masaoi / ARAI et S. Nomura, 2003. Paratypes. 2♂♂1♀ (NSMT), Japan: Saitama Pref. Ranzan town, Ohkura (Tokigawa-riv.), 26-xii-1999, Shiho Arai leg.; 1♂2♀♀ (NSMT), 23-i-2000, Kôji Toyoda leg.; 1♂2♀♀ (NSMT), 29-xii-1999, Shiho Arai leg.; 1♀ (NSMT), 6-xii-1999, Kôji Toyoda leg. Additional material. 1 ♂ (genitalia dissected; CBNUIC), Korea: Chungbuk Prov. Cheongju-si, Seowon-gu, Chungdae-ro 1, CBNU S4-2, 18-iii- 2024, 36°37'30.0"N 127°27'16.6"E, 64 m, sifting leaf litter & soil, T.-Y. Jang.
Sexual dimorphism. Antennomeres 9–11 shorter than in male (Fig. 2D).
Habitat. This species was collected by sifting leaf litter and soil (Fig. 3).
Distribution. South Korea, Japan (Fig. 3).
KSAE
