Pelochares ryukyuensis M. Sato 1966
Year: 2026
Type: article
Abstract: Pelochares ryukyuensis M. Satô, 1966 Pelochares ryukyuensis M. Satô, 1966 - Satô (1966): 57. Type locality: Ryukyu Archipelago (Japan) and Taiwan (China). Materials Type status: Other material. Occurrence: recordedBy: Jiseung Kim; sex: 1 male; lifeStage: adult; occurrenceID: DDB0E4AF-F5A8-5E91-9425-CE2D68EA9652; Taxon: scientificName: Pelochares ryukyuensis; Location: country: South Korea; stateProvince: Jeollanam-do; locality: Muan-gun, Hyeongyeong-myeon, Haeun-ri; decimalLatitude: 35.050821; decimalLongitude: 126.460238; Identification: identifiedBy: Jiseung Kim; Event: eventDate: 18-09-2025; Record Level: institutionCode: JBNU; basisOfRecord: PreservedSpecimen Type status: Other material. Occurrence: recordedBy: Jiseung Kim & Seunghyun Lee; sex: 13 males, 27 females; lifeStage: adult; occurrenceID: 80EAC54B-1F0E-57B9-BFD8-A5235CBB5115; Taxon: scientificName: Pelochares ryukyuensis; Location: country: South Korea; stateProvince: Jeollanam-do; locality: Gwangyang-si, Jinsang-myeon, Jiwon-ri; decimalLatitude: 35.023753; decimalLongitude: 127.721606; Identification: identifiedBy: Jiseung Kim & Seunghyun Lee; Event: eventDate: 20-08-2026; Record Level: institutionCode: JBNU; basisOfRecord: PreservedSpecimen Type status: Other material. Occurrence: recordedBy: Wongun Kim; individualCount: 1; lifeStage: adult; occurrenceID: B7666354-01AC-5556-9BC0-12AC459FDBD1; Taxon: scientificName: Pelochares ryukyuensis; Location: country: South Korea; stateProvince: Jeollabuk-do; locality: Gochang-gun, Asan-myeon, Samin-ri; decimalLatitude: 35.488442; decimalLongitude: 126.575972; Identification: identifiedBy: Jiseung Kim & Seunghyun Lee; Event: eventDate: 24-07-2021; Record Level: basisOfRecord: HumanObservation Type status: Other material. Occurrence: recordedBy: Hyunkyu Park; individualCount: 1; lifeStage: adult; occurrenceID: E8631D0B-5FA8-5A5D-8B14-B225BA8C3399; Taxon: scientificName: Pelochares ryukyuensis; Location: country: South Korea; stateProvince: Jeollabuk-do; locality: Wanju-gun; Identification: identifiedBy: Jiseung Kim & Seunghyun Lee; Event: eventDate: 06-08-2022; Record Level: basisOfRecord: HumanObservation Type status: Other material. Occurrence: recordedBy: Jihwan Park; individualCount: 1; lifeStage: adult; occurrenceID: 5C87415A-3226-52C7-A3B4-38ACC395C7D1; Taxon: scientificName: Pelochares ryukyuensis; Location: country: South Korea; stateProvince: Jeollanam-do; locality: Gwangyang-si, Jinsang-myeon, Jiwon-ri; decimalLatitude: 35.023753; decimalLongitude: 127.721606; Identification: identifiedBy: Jiseung Kim & Seunghyun Lee; Event: eventDate: 30-08-2025; Record Level: basisOfRecord: HumanObservation Diagnosis Body broadly oval and convex; general colouration dark brown to black; dorsal surface clothed with short decumbent setae only (Fig. 1 A and B). The species differs from Limnichus lewisi by the absence of a mixture of decumbent short setae and obliquely erect long setae on the dorsum, scutellum approximately as long as wide rather than distinctly elongate, basal two antennomeres enlarged and apical five antennomeres flattened and loosely connected rather than basal three antennomeres enlarged and apical three antennomeres forming a loose club, terminal antennomere only slightly longer than the preceding antennomere rather than more than twice as long, metacoxa with a distinct transverse groove rather than a row of punctures and apical maxillary palpomere elongate, about three times as long as wide, rather than shorter and broader. Male genitalia are also distinctly different from those of L. lewisi (Ito and Maehara 2017): median lobe of aedeagus as long as parameres, unlike L. lewisi with median lobe much longer than parameres; parameres slightly shorter than phallobase; apex of parameres slightly dilated and well sclerotised (Fig. 1 C – E). Korean specimens: body length 2.01–2.28 mm; body width 1.20–1.41 mm. Distribution Korea (New record), Japan (Honshu, Shikoku, Kyushu, Tsushima, Koshikijima Islands and Ryukyu Islands) and China (Taiwan) (Satô 1965, Satô 1966, Yoshitomi 2007, Ito and Maehara 2017, Yoshitomi 2025). Habitat All Korean occurrence sites currently known were stream margins immediately downstream of reservoirs, where adults were attracted to light (Fig. 2 A and B). In Japan, P. ryukyuensis has been collected near lights, including many individuals attracted to a house light in Higashihiroshima during summer and from flood debris on the Tama River floodplain in Inagi after a typhoon-induced flood (Ito and Maehara 2017). DNA barcode and phylogenetic analyses In the Maximum Likelihood (ML) and Neighbour-Joining (NJ) phylogenetic trees (Fig. 3), the Korean P. ryukyuensis sequence, analysed in this study, formed a conspecific clade with Japanese sequences (accession numbers: LC 866137 – LC 866139). Based on the Kimura 2 - parameter (K 2 P) model, the intraspecific divergence within P. ryukyuensis ranged from 0.15 % to 1.70 % (average: 1.15 %) (Table 1). Additionally, it grouped in the same clade with Pelochares murinus (Baudi, 1870) of the same genus, exhibiting an interspecific divergence ranging from 20.86 % to 21.29 % (average: 21.13 %). This Pelochares clade was completely separated into a distinct clade from Limnichus lederi Weise, 1877 and Limnichus sericeus (Duftschmidt, 1825) of the same subfamily (Limnichinae). Remarks The Korean specimens agree with P. ryukyuensis in external habitus, male genitalia and COI barcode sequence. The combination of voucher examination and molecular confirmation is important because P. ryukyuensis has historically been confused with Limnichus lewisi in Japan (Ito and Maehara 2017). Online records from Gochang-gun and Wanju-gun suggest that P. ryukyuensis may be distributed across south-western Korea. The suggested vernacular Korean name for the species is “ Jan-teol-seup-ji-beol-le ”, referring to the surface clothed with short decumbent setae. Additionally, the suggested vernacular Korean names for the family Limnichidae Erichson, 1846 and the genus Pelochares Mulsant and Rey, 1869 are proposed as “ Seup-ji-beol-le-gwa ” and “ Jan-teol-seup-ji-beol-le-sok ”, respectively.
Authors: Kim, Jiseung, Lee, Seunghyun, Kim, Sora
Institutions: Seoul National University, Jeonbuk National University
Language: English
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W7225645050
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