Leptoplectus uttu, Jałoszyński, 2025

Jałoszyński, Paweł, 2025, Two new species of Euplectini from Ryukyu Islands, Japan (Coleoptera, Staphylinidae, Pselaphinae), Zootaxa 5631 (3), pp. 561-573 : 567-570

Leptoplectus uttu sp. nov.

( Figs 15–28 )

Type material. Holotype: JAPAN (Okinawa Pref.): ♂, two labels: „ JAPAN, OKINAWA Pref. / OKINAWAjima , 31 xii 2024 / Ogimi, Nekumachiji-dake / 26.684151, 128.136069 / leg. P. JAŁOSZYŃSKI ” [white, printed], “ LEPTOPLECTUS / uttu m. / HOLOTYPUS / P. JAŁOSZYŃSKI, 2025 ” [red, printed] ( NSMT).

Diagnosis (male). Body light reddish brown; head distinctly broader than pronotum and weakly transverse; Ushaped sulcus connecting dorsal tentorial pits anteriorly shallow; vertex posteromedially with shallow subtriangular impression; antennomere 11 distinctly more than 1.5 times as long as broad; prothorax weakly transverse, with shallow constriction distinctly 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 slightly elongate; abdominal tergites IV and V each with strongly divergent discal carinae, those on IV clearly longer than half length of tergite, those on V subequal to half length of tergite; aedeagus in dorsal view with three asetose apical projections: two short, slender, subtriangular on left side directed mesad and one long and broad projection on right side parallel to the long axis of aedeagus and with broadly rounded apex; basal capsule of aedeagus asymmetrical and with basal margin lacking basal process.

Description. Body of male ( Fig. 15 ) slender and flattened, uniformly light reddish brown, setae lighter than cuticle, cuticle moderately glossy; BL 1.19 mm.

Head ( Figs 15–18 ) 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, lateral margins of frontovertexal region strongly converging anterad; frontal region with anterior portion not thickened and demarcated at each side from supraantennal region by shallow and diffuse slightly oblique groove mesally connected with U-shaped frontovertexal sulcus; the latter shorter than half length of head, complete but with shallow anterior region; dorsal tentorial pits round, each filled with several lanceolate setae; median region of frontovertexal area delimited by U-shaped sulcus weakly convex; eyes moderately large, strongly convex and coarsely faceted; tempora in dorsal view slightly longer than eye length. Setiferous punctures on frontovertexal region fine and sharply marked, almost evenly and relatively densely distributed except for impunctate 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.

Labrum ( Figs 18–19 ) with lateral lobes irregular in shape, each with distinct angulate anterolateral emargination, so that anterolateral regions of labrum form sharp-angled but blunt corners.

Genal region in ventral view ( Fig. 16 ) covered with similar punctures and setae as median region of head dorsum.

Antennae ( Fig. 20 ) distinctly shorter than head and pronotum together; AnL 0.35 mm; scape slightly transverse; pedicel slightly narrower than scape, weakly elongate; antennomeres 3–10 each distinctly transverse and from 9 gradually broadening; antennomeres 9–11 forming distinct club, 9 and 10 ( Fig. 21 ) each with several longitudinal elongate impressions separating convex areas, so that antennomeres have an appearance of a flower, antennomere 11 strongly elongate and much 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, apex of antennomere 11 with deep cavity bearing large cluster of basiconic sensilla.

Pronotum ( Fig. 17 ) rounded, broadest distinctly anterior to middle; PL 0.24 mm, PW 0.25 mm. Anterior margin nearly straight at middle; lateral margins sinuate in anterior third, then strongly convex, slightly constricted behind middle, and just in front of posterior corners sinuate; posterior margin weakly and evenly arcuate. Pronotal disc with incomplete median longitudinal sulcus developed as short and shallow elongate impression in front of middle; pronotum with pair of large and relatively deep lateral antebasal foveae filled with sparse lanceolate setae, and with shallow and diffuse round and asetose median antebasal fovea; foveae connected by very 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, lateral margins near posterior 1/4 with a few flattened and distally broadening setae.

Prosternum ( Fig. 16 ) with fine and sparse setiferous punctures on median area flanked by smooth asetose regions. Pair of foveae in front of procoxae filled with a few lanceolate setae.

Mesoscutellar shield largely hidden under posterior pronotal margin, only barely discernible narrow subtriangular tip exposed between elytral bases.

Elytra ( Fig. 17 ) together subrectangular with weakly rounded sides, broadest slightly behind middle; EL 0.35 mm, EW 0.33 mm. Each elytron with complete sutural sulcus, one short and diffuse discal sulcus in slightly less than anterior 1/3, three dorsal basal elytral foveae, and one lateral fovea not visible in dorsal view and situated just behind rounded off posthumeral denticle. Posterolateral elytral corner weakly 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 on elytra finer than those on pronotal disc, inconspicuous; setae similar to those on pronotum.

Hind wings well developed, functional.

Mesoventrite ( Fig. 16 ) 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 reticulate microsculpture except for posteromedian suboval area, which bears several short setae; two lateral mesoventral foveae filled with a few flattened and broadened setae; single small median mesoventral fovea in Fig. 16 obscured by procoxae.

Metaventrite ( Fig. 16 ) distinctly transverse and weakly convex at sides, with shallow and diffuse median longitudinal groove, anterior metaventral process short, subtriangular. Two pairs of metaventral foveae (laterad and posterad each mesocoxa) filled with a few flattened and broadened 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. 16 ) short and robust, protarsi slightly shorter than meso- and metatarsi; legs unmodified.

Abdomen ( Figs 15–16 , 22–24 ) slightly longer than elytra, AbL 0.38 mm, AbW 0.30 mm. Tergites IV–VI subequal in length, VII slightly longer than VI; tergites IV–V each with sharply marked discal carinae strongly diverging posterad, those on IV longer than half length of tergite, those on V about as long as half length of tergite, carinae separated by large fovea filled with lanceolate setae, distance between posterior ends of discal carinae much wider than 1/3 of tergite without laterotergites. Tergite VIII unmodified, with rounded posterior margin. Hemitergites IX shifted ventrad ( Fig. 23 ) 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. 16 ) with large transverse metacoxal rests each posteriorly demarcated by sinuate carina and microreticulate, metacoxal rests separated at middle by large, elongate median process broadening posterad, 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 slightly longer than V and VI; sternite VII ( Figs 23–24 ) unmodified, except for submedian lateral groups of campaniform sensilla, in microscope slide ( Fig. 24 ) appearing as groups of ‘pseudopores’. Surface of sternites covered with punctures and setae similar to those on tergites.

Aedeagus ( Figs 25–28 ) elongate and strongly asymmetrical; AeL 0.18 mm; median lobe in dorsal view with three asetose apical projections: two short, slender, subtriangular on left side directed mesad and one long and broad projection on right side parallel to long axis of aedeagus and with broadly rounded apex; basal capsule of aedeagus asymmetrical and with basal margin lacking basal process.

Female. Unknown.

Distribution. Okinawa-jima Island, Okinawa Prefecture, Ryukyu Archipelago, Japan.

Etymology. In Uchinaaguchi, the language of Okinawa Island, uttu means a younger sibling (noun in apposition). Leptoplectus uttu is a “younger” sibling of the previously described Okinawan L. kijimunaa .

Remarks. Leptoplectus uttu is slightly larger than its Okinawan congener L. kijimunaa , and uniformly reddish brown (in L. kijimunaa the elytra are usually infuscate). These species can be easily distinguished also by a set of conspicuous features: the head in L. uttu is distinctly broader than the pronotum and almost as broad as the elytra (in L. kijimunaa the head as broad as the pronotum and distinctly narrower than the elytra); antennomere 11 more than 1.5 times as long as wide (in L. kijimunaa less than 1.5× as long as wide); the aedeagus in dorsal view with one broad, apically rounded right distal projection and without setae (in L. kijimunaa there are four right distal projections, each slender, and median lobe with a transverse row of long setae). All the remaining nominal species of Leptoplectus recorded from Japan and closely adjacent islands occur north-east of the Ryukyus. Leptoplectus nipponensis that occurs in Shikoku ( Jeannel 1958) has the basal capsule much shorter in relation to the distal region of the median lobe, the distal projections on the left side parallel to the long axis of the aedeagus and the right distal projection of a different shape and much longer than that in L. uttu . Leptoplectus pumilio occurring in Kyushu ( Nomura 2023b) has the distal region of the median lobe distinctly trilobate, with the median lobe broader and much longer than the remaining lateral lobes. Leptoplectus remyi known in Japan from a single specimen collected in Honshu ( Nomura 2004) has an almost circular basal capsule in dorsal view, a short and slender right distal projection and lacks left distal projections. Three species found on the Kuril Archipelago, that is L. perperus , L. similis , and L. solivagus , also have clearly different aedeagi: L. perperus and L. similis have a long basal process of the basal capsule, lacking in L. uttu , and a different set of distal sclerites, while L. solivagus has a left distal projection much longer than the remaining ones.

Figures

FIGURES 15–16. Leptoplectus uttu sp. nov., male. Dorsal (51) and ventral (16) habitus.

FIGURES 17–21. Leptoplectus uttu sp. nov., male. Head and thorax in dorsal view (17), anterior frontal region and mouthparts in anterodorsal view (18), labrum in anterodorsal view (19), left antenna in dorsal view (20), and antennomeres 9 and 10 in dorsal view (21).

FIGURES 22–28. Leptoplectus uttu sp. nov., male. Abdomen in dorsal view (22), posterior region of abdomen in ventral view (23), sternites VII–VIII (24), and aedeagus in dorsal (25, 27), and lateral (26, 28) views.