The family Histeridae comprises about 400 genera and 4,800 species belonging to nine subfamilies (Zhou et al., 2020;Newton et al., 2025). They are generally predaceous beetles, exhibiting various ecological adaptations, such as microhabitats (Penati, 2009). One of the notable lifestyles of the histerids is the inquilinous habit (an association with other organisms such as mammals, birds, and various social insects), which is prevalent across various histerid subfamilies (Kovarik and Caterino, 2000, 2016;Bousquet and Laplante, 2006;Penati, 2009).

Two of a total of nine subfamilies, Haeteriinae and Chlamydopsinae, are exclusively associated with social insects, particularly ants and termites (Parker, 2016). The members of Chlamydopsinae are most abundant and diverse in the Australasian region, with some species occurring in the Oriental region, while Haeteriinae exhibit high species diversity in the Neotropical region (Mazur, 1997, 2011;Caterino, 2000;Kovarik and Caterino, 2016;Caterino and Dégallier, 2007;Tishechkin and Caterino, 2007). Among them, the members of Chlamydopsinae have not yet been reported from Korea, whereas a single species of Haeteriinae is recognized (Kim and Lim, 1997;NIBR, 2019).

The genus EucurtiopsisSilvestri, 1926, one of the chlamydopsine genera, comprises 27 described species (Mazur, 2011;Théry, 2021). This genus was first described with E. mirabilis from Taiwan (Silvestri, 1926), and two additional species were subsequently described from Japan (Sawada, 1994;Nishikawa, 1995). Thus, this genus was regarded as a northern chlamydopsine lineage until numerous species were described from the Malay Archipelago (Borneo, Sulawesi, and the Philippines) and, especially, Melanesia (Vanuatu) by several authors (Caterino, 2000;Dégallier and Caterino, 2005;Caterino and Dégallier, 2007;Tishechkin and Caterino, 2007;Tishechkin, 2009).

Eucurtiopsis is defined by the following features: i) width of pronotum n arrower than t hose o f elytra; ii) p ronotum w ith paired subapical dorsal processes; iii) scutellum invisible; iv) elytral trichome transversely incised (Silvestri, 1926;Caterino and Dégallier, 2007;Tishechkin and Caterino, 2007;Tishechkin, 2009). Among the species, only Eucurtiopsis ohtanii (Sawada, 1994) from Japan has known ecological data, with Pheidole fervida Smith as its host (Ôhara, 1994;Nishikawa, 1995).

In the present study, we collected a myrmecophilous Eucurtiopsis species, E. ohtanii, by sifting the mass of a Pheidole fervida colony from Jeju Island. We report the new distributional record of this remarkable species from Korea for the first time, providing a diagnosis for the species, photographs of the adults, and some ecological information.

Materials and Methods

During the faunal survey on Jeju Island in 2022, one of the authors collected a single individual of Eucurtiopsis ohtanii from a Pheidole fervida colony.

The collected specimen was preserved in 95% ethanol and made into dried specimens for exact identification. Photographs of the specimen were taken with a digital camera (EOS-90D, CANON, Japan) through MP-E 65 mm lens. Several image layers were stacked by the software (Zerene Stacker 1.04, Zerene Systems, USA). A single specimen used in this study is deposited in the insect collection of the National Institute of Biological Resources (NIBR, Incheon, Korea). Terminology and morphological concepts used in present study mostly follows Ôhara (1994).

Taxonomic Accounts

Family Histeridae Gyllenhal, 1808

Subfamily Chlamydopsinae Bickhardt, 1914 고리어깨풍뎅 이붙이아과(신칭)

Genus EucurtiopsisSilvestri, 1926 고리어깨풍뎅이붙이속 (신칭)

EucurtiopsisSilvestri, 1926: 265. Type species: Eucurtiopsis mirabilisSilvestri, 1926: 268.

BoreochlamydusSawada, 1994: 357. Type species Boreochlamydus ohtaniiSawada, 1994: 359.

Diagnosis. Body: most of surface covered with setae. Head: deeply retractable into prothorax; frons laterally parallel-sided with lateral marginal stria; antennal club without annuli or sutures. Prothorax: pronotum narrower than elytra; pronotum with paired dorsal tubercles near pronotal apex. Pterothorax: scutellum invisible; elytral trichome distinctly developed posterad from humeral angle, with transverse incision (Silvestri, 1926;Caterino and Dégallier, 2007;Tishechkin and Caterino, 2007;Tishechkin, 2009).

Eucurtiopsis ohtanii (Sawada, 1994) 고리어깨풍뎅이붙이 (신칭)

Boreochlamydus ohtanii Sawada, 1994: 359.

Diagnosis. Body 1.8 mm long and 1.2 mm wide; oblong and fairly convex; surface mostly shining castaneous, with ferruginous antennae and legs; surface partially covered with various series of yellow setae (Figs. 1A–D). Head with surface (Fig. 1F) densely covered with large, coarse, and umbilicate punctures; anterior margin of epistome almost truncate; labrum semicircular; antennal scape large, elongate, apically elbowed, and covered with long setae on coarse outer surface; antennal club elongate and densely covered with setae. Pronotum (Fig. 1E) pentagonal, convex; disc distinctly elevated at anteromedial part, with a longitudinal depression on midline; with a pair of tubercles on each anterior angle; surface covered with large, coarse, and umbilicate punctures, intermingled with fine punctures, and densely covered with long setae. Scutellum invisible. Elytra (Fig. 1C) with a paired distinct humeral trichome; anterior and posterior elevations completely separated by transverse ridge; anterior elevation with two longitudinal excavations on dorsum; medial parts of surface mostly glabrous with a few rows of punctures along elytral suture on basal half; disc covered setiferous punctures with a paired longitudinal glabrous region near elytral suture on apical half; elytral sutural stria complete. Propygidium (Fig. 1G) pentagonal, convex; deeply punctate with regular-sized setiferous punctures. Pygidium covered with punctures similar to those of propygidium. Prosternum convex and wide; slightly bisinuate at anterior margin; surface covered with irregular-sized punctures with setae; prosternal process wide, almost quadrate. Mesoventrite short and broad; broadly bi-concaved at anterior margin; surface covered with large and coarse punctures; lateral disc glabrous, deeply excavate to receive mesotibia. Metaventrite with a distinct medio-longitudinal groove; surface irregularly punctate with short setae, usually larger and denser marginally. Abdomen with five visible ventrites; abdominal ventrite 1 punctate as metaventrite, with lateral deep excavations to fit metatibia; each ventrite covered with distinct setiferous punctures, coarser and denser laterally. Legs with setose femora and tibiae; femora stout; protibia (Fig. 1H) smoothly angulate on basal one-third, meso- and metatibia angulate near middle. Male genitalia shown as Fig. 1 (Figs. 1I–N); aedeagus dorsoventrally flattened, bent ventrally near apex; ratio in length of paramere to basal piece of aedeagus about 0.35.

Specimens examined. 1♂, Sanghyo-dong, Seogwipo-si, Jeju Island, 25.V.2022, leg. K. Go, collected from a nest of Pheidole fervida Smith.

Distribution. Korea (new record), Japan

Remarks.Eucurtiopsis ohtanii can be easily distinguished from other Korean histerids by its distinct antennal scape, pronotal tubercles, and humeral trichome on the elytra. The host range is very specific and the only known host ant species is Pheidole fervida Smith. This species was also collected from a nest of P. fervida from Jeju Island, Korea. Several additional observations of this species have been shared in communities with the same host information. Interestingly, although this species moves by itself in the ant colony, an individual was observed in Jeju Island being carried by workers and soldiers of P. fervida, which grasped the beetle’s distinct humeral trichome between anterior and posterior elevations of elytron (Figs. 2B–C) (personal communication with Mr. Yoon, Sun- woo). This behavior implies that the trichomes, which are typically grasped by ants, are useful structures for myrmecophilous insects to communicate and interact with ants, regardless of whether the mechanism is chemical or physical.

This species has been reported from Kyushu and the southern part of Honshu, as well as from one of the Japanese oceanic islands, Hachijō-jima (Nishikawa and Fukuzawa, 2010). In addition, all members of Eucurtiopsis are known to be distributed along the Pacific Islands (Mazur, 2011). Thus, a new record from Jeju Island is consistent with the previously known distribution patterns in the broad sense and provides new insight into the biogeography across the genus.