Sindosium longifilum sp. nov.

(Figs 1C–D, 3, 5: triangle)

Diagnosis. The adult of Sindosium longifilum can be distinguished from other Sindosium species by an unusually prolonged seta on the last anterior serration of the elytral humeri and oval spermatheca with pointed basal tip.

Description. Body length 0.95–1.00 mm, width 0.53–0.55 mm; oval, convex; color reddish brown, evenly punctuate with pale yellow pubescence.Antennomeres I–II light reddish brown, III–XI reddish yellow (Figs. 1C–D).

Head. Broad, rounded; weakly, finely, sparsely punctuate. Eyes large; distance between eyes in ventral view 0.19 mm. Antennal length 0.42 mm; Antennomeres I–II large, thicker than others; III short, cone-shaped; IV–VII long, weakly swollen distally; VIII slightly shorter; IX–XI clavate, basal half of seta darker; IX ovoid; X basal half swollen; XI ovoid (Fig. 3A).

Thorax. Pronotum length 0.30 mm, width 0.49 mm; widest slightly behind middle; lateral margin serrated, flattened, curved, and basally narrowed; surface shining, rather weakly, evenly punctuate with pubescence; posterior margin wider than anterior (Fig. 3B). Scutellum equilaterally triangular (Fig. 3C).

Wings. Elytral length 0.69 mm, long, complete; rather weakly, evenly punctuate with pubescence; lateral margin serrate anteriorly, with 4–5 denticules, each with long seta, posterior one conspicuously long; posterior margin rounded (Fig. 3E). Hindwing blade wide, membranous; anterior petiolar margin with one distinct seta, posterior margin setose on distal half (Fig. 3D).

Meso-, Metaventrite. Mesoventrite anteriorally with prominent collar and keel; keel wider than median extension of collar; laterally of mesocoxae, mesopleural [anterior] suture straight, directed obliquely anterad, metaventral [posterior] line rather straight, distally obtusely angled, directed posterad. Mesoventrite medially shorter than metaventrite (Fig. 3G).

Abdomen. Abdominal sternite I anteromedially with prominent knob fitting to metaventral [intermetacoxal] condyle (Figs. 3G, J–K). Tergite X small, in male trapezoid, in female semicircular (Figs. 3H–I).

Legs. Male foreleg with pubescence around tarsus (Fig. 3F). Procoxae contiguous. Mesocoxae separated by arrow-shaped process. Metacoxae short, wide, almost contiguous, only separated by an intermetacoxal condyle (Figs. 3B, G).

Male genitalia. Aedeagus elongate, flattened, slightly asymmetric, basal foramen skewed, apex angular. Each paramere with three setae, apical one longer (Fig. 3L).

Female genitalia. Spermatheca length 0.15 mm, width 0.087 mm; oval, slightly longer than broad, basal tip pointed with chord, mushroom-shaped part short and stout (Fig. 3M).

Material examined (n=36, 16♁♁ 20♀♀).

Holotype (deposited in NIBR), ♁ (dry), Korea: Gyeonggi Prov. Bogwangsa, 87, Bogwang-ro 474beon-gil, Gwangtan-myeon, Paju-si, 15.V.2021, 37°45′06″N 126°54′56″E, 190 m, sifting leaf & soil litter, J.-W. Seo.

Paratypes (deposited in CBNUIC), 1♁ (dry), same data as in holotype; 2♁♁ 2♀♀ (2♁♁, dry; 2♀♀, slide), Korea: Chungbuk Prov. Gaesin-dong, Heungdeok-gu, Cheongju-si, 01.IV.2020, 36°37′43.5″N 127°27′16.7″E, 75 m , sifting leaf & soil & deadwood debris, M.-S. Jang, J.-Y. Kang, Y.-J. Choi, T.-Y. Jang, U.-J. Byeon, J.-W. Kim; 1♀ (dry), Korea: Chungbuk Prov. Jagwangsa, Mt. Worak, 1560-35, Mireuksonggye-ro, Hansu-myeon, Jecheon-si, 28. V.2020, 36°52′52.0″N 128°05′10.0″E, 262 m , sifting leaf & soil litter, M.-H. Song, U.-J. Byeon; 3♀♀ (2♀♀, dry; 1♀, slide), Korea: same locality, date, method and collector, 36°52′53.0″N 128°05′08.0″E, 243 m; 1♀ (dry), same locality, 25. V.2021, 36°52′53.3″N 128°05′11.6″E, 270 m, sifting soil litter & flood debris, J.-W. Kang, Y.-J. Choi, M.-H. Song; 2♀♀ (dry), Korea: Chungbuk Prov. Simbok Valley, 95, Yeonpung-ro galgeum 3-gil, Yeonpung-myeon, Goesan-gun, 30. V.2021, 36º46'49.44"N 127º57'45.00"E, 270 m , sifting leaf & soil litter, J.-W. Seo; 1♁ (dry), Korea: Gangwon Prov. Joldeulu-gil, Bukpyeong-myeon, Jeongseon-gun, 27.X.2019, 37°26′54.6″N 128°38′21.0″E, 312 m , sifting leaf & soil litter near stream, M.-S. Jang, J.-W. Kang, U.-J. Byeon; 1♁ (dry), Korea: Gyeongbuk Prov. Seonghyeon-gil, Yongmun-myeon, Yecheon-gun, 04. V.2019, 36°40′48.0″N 128°25′09.0″E, 134 m , sifting leaf & soil litter, U.-J. Byeon; 1♁ (dry), Korea: Gyeonggi Prov. Hoguk-ro 550beon-gil, Jangheungmyeon, Yangju-si, 08.VII.2019, 37º42'38"N 126º58'55"E, 150 m , sifting leaf litter & deadwood debris, Y.-J. Choi, T.-Y. Jang; 4♁♁ (3♁♁, slide; 1♁, in 95% EtOH), Korea: Jeju Island. 137, Donnaeko-ro, Seogwipo-si, 26.IX.2021, 33°17'59.8"N 126°34'59.3"E, 263 m , sifting leaf & soil litter, J.-W. Kang, T.-Y. Jang; 2♀♀ (dry), same locality, date and method, J.-W. Kang, U.-J. Byeon; 1 ♁ 1♀ (in 95% EtOH), Korea: Jeju Island. 516-ro, Namwon-eup, Seogwipo-si, 26.VIII.2021, 33°19'57.9"N 126°36'25.2"E, 504 m , sifting soil & deadwood debris, J.-W. Kang, J.-W. Kim, J.-I. Shin; 3♀♀ (dry), same locality, 26.IX.2021, 33°20'53.6"N 126°36'50.8"E, 601 m, sifting leaf & soil & deadwood debris, J.-W. Kang, T.-Y. Jang; 2♁♁ (slide), Korea: Jeju Island. Mt. Halla, 1100-ro, Aewol-eup, Jeju-si, 28.XI.2021, 33°22'37"N 126°28'06"E, 1012 m , sifting leaf & soil litter, J.-W. Kang, M.-H. Song, J.-I. Shin; 1♀ (dry), Korea: Jeonnam Prov. Mt. Doksil, Gageo island, Gageodo-gil, Heuksan-myeon, Sinan-gun, 07.VII.2020, 34°03′48.4″N 125°07′21.0″E, 366 m , sifting leaf & soil litter, M.-H. Song; 2♀♀ (dry), same locality, 08.VII.2020, 34°04′59.0″N 125°06′21.0″E, 474 m, sifting leaf & soil litter, T.-Y. Jang; 1 ♁ 1♀ (slide), same locality, 19.IV.2021, 34°05'13.3"N 125°06'17.1"E, 415 m, sifting leaf & soil litter near rock, J.-W. Kang; 1♀ (dry), Korea: Jeonnam Prov. Gogeum Island, 102, Cheonghakdong-gil, Gogeum-myeon, Wando-gun, 07.VII.2022, 34°25'18.6"N 126°48'19.5"E, 31 m , sifting leaf & soil litter, S.-H. Choi, J.-W. Seo, U.-J. Byeon; 1♁ (dry), Korea: Jeonnam Prov. Yaksan Island, 566, Yaksanilju-ro, Yaksan-myeon, Wando-gun, 07.VII.2022, 34°21'44.3"N 126°55'00.5"E, 109 m , sifting leaf & soil litter, S.-H. Choi, J.-W. Seo, U.-J. Byeon.

Distribution. South Korea (Fig 5: triangle).

Etymology. The Latin adjective stem “long-” (long) and noun “filum” (filament) refers to the longest seta on the elytra.