Euplectus eemanchu Jałoszyński, 2025, sp. nov.
Creators: name: Jałoszyński, Paweł
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Staphylinidae
Euplectus
Euplectus eemanchu

description: Euplectus eemanchu sp. nov.
(Figs 1–14)
Type material. Holotype: JAPAN (Okinawa Pref.): ♂, two labels: „JAPAN, OKINAWA Pref. / ISHIGAKI Is., Mt. OMOTO / 17 IX 2003 / leg. P. JAŁOSZYŃSKI ” [white, printed], “ EUPLECTUS / eemanchu m. / HOLOTYPUS / P. JAŁOSZYŃSKI, 2025 ” [red, printed] (NSMT).
Diagnosis (male). Body light reddish brown; head distinctly narrower than pronotum and transverse; U-shaped sulcus connecting dorsal tentorial pits deep and continuous; anterior portion of frontal region strongly thickened and forming transverse convexity entirely demarcated by anteromedian region of U-shaped sulcus and laterally by narrow transverse postantennal grooves; vertex posteromedially with shallow subtriangular impression; prothorax strongly transverse, with distinct constriction slightly behind middle; dorsal area along posterior pronotal margin with dense, large but shallow punctures much more distinct than those on remaining pronotal disc; elytra together as long as broad; abdominal tergites IV and V each with strongly divergent discal carinae as long as half length of each tergite; tergite VIII with shallow posteromedian emargination; legs unmodified except for robust mesotibial apical tooth; aedeagus in dorsal view with strongly setose distal outer left projection, submedian sclerite with bifurcate apex and large distal outer right projection; basal capsule of median lobe not narrowing distally; distal projections of median lobe with curved tubular structure projecting distally.
Description. Body of male (Fig. 1) slender and flattened, uniformly light reddish brown, setae lighter than cuticle, cuticle moderately glossy; BL 1.38 mm.
Head (Figs 1–4) subtrapezoidal, broadest at eyes, HL 0.23 mm, HW 0.28 mm. Vertexal region posteriorly arcuate and concave, with small and shallow posteromedian subtriangular impression bearing fine median longitudinal carina; lateral margins of frontovertexal region strongly converging anterad; frontal region with anterior portion forming strongly thickened transverse convexity posteriorly demarcated by anterior region of U-shaped frontovertexal sulcus (medially) and by postantennal transverse grooves (laterally); U-shaped frontovertexal sulcus slightly longer than half length of head, complete and equally deep on entire length, posteriorly ending in round dorsal tentorial pits, each filled with several lanceolate setae; median region of frontovertexal area delimited by Ushaped sulcus weakly convex, frontovertexal region posterolaterad each dorsal tentorial pit slightly flattened; eyes moderately large, strongly convex and coarsely faceted; tempora in dorsal view slightly shorter than eye length. Setiferous punctures on frontovertexal region fine and sharply marked, unevenly and sparsely distributed except for almost impunctate anterior frontal convexity, frontovertexal sulcus and dorsal extension of occipital constriction separating vertex from occiput; exposed anterodorsal region of occiput with transverse microreticulation. Setae short and sparse, suberect.
Genal region in ventral view (Fig. 2) covered with similar punctures and setae as those on median region of head dorsum; submental carina short and narrow.
Antennae (Fig. 5) slightly shorter than head and pronotum together; AnL 0.39 mm; scape slightly elongate; pedicel distinctly narrower than scape, weakly elongate; antennomeres 3–10 each distinctly transverse and from 9 gradually broadening; antennomeres 9–11 forming distinct club, 11 distinctly elongate and clearly longer than 9–10 combined. Antennomeres 1–8 each sparsely and unevenly covered with long setae; antennomeres 9–11 each with setae distinctly denser than on remaining antennomeres.
Pronotum (Fig. 3) rounded, broadest slightly anterior to middle; PL 0.25 mm, PW 0.31 mm. Anterior margin weakly arcuate behind head; lateral margins strongly rounded, slightly behind middle slightly constricted, lateral margins just in front of posterior corners slightly sinuate; posterior margin distinctly arcuate but with straight median portion. Pronotal disc with incomplete median longitudinal sulcus developed as short and shallow elongate impression in front of middle and even less distinct posterior longitudinal impression behind median antebasal fovea; pronotum with pair of large and relatively deep lateral antebasal foveae filled with sparse lanceolate setae, and with almost punctiform deep round median antebasal fovea; foveae connected by shallow and diffuse slightly biarcuate antebasal groove. Pronotal disc nearly evenly covered with punctures similar to those on frontovertexal region, except for dorsal area along posterior pronotal margin with dense, large but shallow punctures much more distinct than those on remaining pronotal disc. Vestiture of pronotal disc composed of sparse, short and weakly suberect setae.
Prosternum (Fig. 2) with fine and sparse setiferous punctures except for dense transverse row of large but shallow and diffuse punctures along its anterior crenulate margin. Pair of foveae in front of procoxae densely filled with setae.
Mesoscutellar shield largely hidden under posterior pronotal margin, only barely discernible narrow subtriangular tip exposed between elytral bases.
Elytra (Fig. 3) together slightly subtrapezoidal with rounded sides, broadest slightly behind middle; EL 0.40 mm, EW 0.40 mm. Each elytron with complete sutural sulcus, one short and diffuse discal sulcus in slightly less than anterior half, four dorsal basal elytral foveae of which one outermost is closer to anterior elytral margin than remaining three, and one lateral fovea not visible in dorsal view and situated just behind blunt posthumeral denticle. Posterolateral elytral corner obtuse-angled and blunt; posterior elytral margin just mesad posterolateral corner distinctly emarginate, mesally nearly straight; posterior sutural corner with small acute subtriangular projection. Punctures and setae on elytra similar to those on median region of pronotal disc.
Hind wings well developed, functional.
Mesoventrite (Fig. 2) transverse, with lateral regions fully demarcated from metaventrite. Mesoventral intercoxal process subtriangular, elongate, posteriorly overlapped by anterior metaventral process. Subtriangular area posterior to mesoventral procoxal rests covered with minute setae; three mesoventral foveae densely filled with setae (median fovea is composed of two separate pockets with openings situated in single impression filled with setae, externally appearing as single fovea).
Metaventrite (Fig. 2) distinctly transverse and weakly convex at sides, with sharply marked median longitudinal groove, anterior metaventral process narrow and elongate. Two pairs of metaventral foveae (laterad and posterad each mesocoxa) filled with dense setae. Anterolateral regions laterad mesocoxae impressed, impunctate and asetose (possibly metanepisternum fused with metaventrite, but still demarcated by elongate impression); metaventrite covered with punctures and setae similar to those on pronotal disc.
Legs (Fig. 2) short and robust, profemora slenderer than meso- and metafemora, protarsi shorter than meso- and metatarsi; legs unmodified except for robust distal tooth on each mesotibia.
Abdomen (Figs 1–2, 6–10) distinctly longer than elytra, AbL 0.50 mm, AbW 0.38 mm. Tergites IV–VI subequal in length, VII distinctly longer than VI; tergites IV–V each with sharply marked discal carinae as long as half length of tergite and strongly diverging posterad, carinae separated by large fovea filled with lanceolate setae, distance between posterior ends of discal carinae subequal to 1/3 of tergite without laterotergites. Tergite VIII (Fig. 8) small, with rounded and medially emarginate posterior margin. Hemitergites IX shifted ventrad (Figs 7, 10) subtriangular and slightly asymmetrical. Surface of exposed tergites and laterotergites relatively sparsely covered with punctures and setae similar to those on elytra. Sternite III (Fig. 2) with large transverse metacoxal rests each posteriorly demarcated by arcuate carina and finely longitudinally rugose in anterior half, metacoxal rests separated at middle by large, elongate median process broadening posterad and again narrowing in short posterior area, postcoxal regions of sternite III with dense fringes of posteriorly-directed setae covering anterolateral impressions on sternite VI. Sternite IV subequal in length to III and much longer than V and VI; sternite VII (Figs 7, 9) medially emarginate anteriorly and posteriorly. Surface of sternites covered with punctures slightly deeper than those on tergites, similarly dense, setae similar to those on tergites.
Aedeagus (Figs 11–14) elongate and strongly asymmetrical; AeL 0.25 mm; median lobe in dorsal view with asymmetrical and elongate basal capsule; distal portion of aedeagus demarcated by abrupt broadening, strongly asymmetrical, bearing three elongate projections: strongly setose distal outer left projection with apex curved mesad, submedian sclerite with bifurcate apex curved towards left projection, and large distal outer right projection, which is the longest and most complex in shape, bearing strongly curved tubular structure projecting distally.
Female. Unknown.
Distribution. Ishigaki-jima Island, Okinawa Prefecture, Ryukyu Archipelago, Japan.
Etymology. In Uchinaaguchi, the language of Okinawa Island, Eema (or Yeema) is the name of the Yaeyama Islands, an archipelago where Ishigaki Island is located. Eemanchu (or Yeemanchu) is an inhabitant of these islands (noun in apposition).
Remarks. The holotype of E. eemanchu was collected on Mt. Omoto-dake, near its base, by sifting leaf litter.
Four species of Euplectus have been previously recorded from Japan, but none of them are known to occur in the Ryukyus. Euplectus domefactus was found in Honshu, E. doryphorus in Kyushu and Shikoku, E. rubicundus in Honshu, Kyushu and on the Gotô Islands, and E. sawadaianus occurs in Honshu. In addition, the broadly distributed European-Siberian E. punctatus is known to occur on the Kurile Islands, and it cannot be excluded that this species may be present also on the Japan mainland. The aedeagi of all of these species, and those described by Kurbatov from the Russian Far East, have been illustrated, except for one. Euplectus sawadaianus remains the only eastern Palaearctic species whose aedeagus has never been illustrated, and the holotype male has not been dissected (email from S. Nomura dated 23.02.2025). The holotype was illustrated in Nomura (2001), and I have in my collection a single specimen collected on Mt. Kunimidake, Fukui Prefecture, Honshu, on 26.04.2003, identified by S. Nomura as E. sawadaianus. Euplectus eemanchu is slightly larger than E. sawadaianus, has the head clearly narrower than the pronotum (subequal in width in E. sawadaianus), the pronotum more transverse, with a short but distinct longitudinal median groove just behind the median antebasal fovea (lacking in E. sawadaianus), and with distinctly longer discal carinae on abdominal tergites IV and V.
description: Published as part of Jałoszyński, Paweł, 2025, Two new species of Euplectini from Ryukyu Islands, Japan (Coleoptera, Staphylinidae, Pselaphinae), pp. 561-573 in Zootaxa 5631 (3) on pages 562-566, DOI: 10.11646/zootaxa.5631.3.9, http://zenodo.org/record/15371285