Syleter gradus, Balkenohl, 2021

Balkenohl, Michael, 2021, Revisiting the Oriental genus Syleter Andrewes, 1941 (Coleoptera: Carabidae: Clivinini), Revue suisse de Zoologie 128 (2), pp. 357-374 : 368-369

publication ID	https://doi.org/ 10.35929/RSZ.0050
DOI	https://doi.org/10.5281/zenodo.5640148
persistent identifier	https://treatment.plazi.org/id/014C8648-FFE6-BB3B-3077-752BFD40F973
treatment provided by	Felipe
scientific name	Syleter gradus
status	sp. nov.

Treatment

Syleter gradus sp. nov.

Figs 13 View Figs 7-13 , 20 View Figs 14-20 , 27 View Figs 21-27

Holotype: BMNH; ♂, white, handwritten in black ink “ Talang Borneo Grabowsky I. 82”, black printed “ H.E.Andrewes Coll. B.M. 1945-97.”, white, black handwritten and printed “ Psilus acutipalpis Putz. Compared with type H.E.A.”, black printed “ H.E.Andrewes Coll. B.M. 1945-97.”.

Paratypes: BMNH; 1 ♀, white, handwritten in black ink “ Talang Borneo Grabowsky”, black printed “ H.E. Andrewes Coll. B.M. 1945-97.” . – ADCW; 5 ♀♀, with labels and data: white, black printed “ INDONESIEN: Kalimantan Timur, Tanjung Isuy 20.1.1995 leg. Seyfert & Greindl (33)”, orange, handwritten “Coll. Zettel Wien” .

Diagnosis: A larger sized species with seven-setose labrum, and the clypeus and frons isodiametrically reticulated. Differentiated from the similar species S. paradoxus and S. sinepunctatus sinepunctatus sp. nov. by the stepped and complete neck constriction, the longitudinal reticulation of the intervals one to seven, and the larger size. In addition, in S. sinepunctatus sinepunctatus sp. nov. the punctures on the disk of the pronotum are missing, and in S. paradoxus the clypeus is not reticulated.

Etymology: The name is a noun and refers to the stepped neck constriction (Latin: gradus – step).

Description

Measurements: Body length 4.25-4.66 mm (x = 4.41 mm *), width 1.32-1.55 mm (x = 1.46 mm *), ratio length/width of pronotum 0.99-1.02 (x = 1.01*), ratio length/width of elytra 1.62-1.72 (x = 1.67*); (*n = 7).

Colour: Piceous to fuscous. Intermediate and hind leg fuscous. Antenna, tarsomeres and palpomeres testaceous. Head: A third narrower than pronotum, frons and clypeus anterior eye-level conspicuously elongated. Clypeus straight anteriorly, with lateral angle obtuse rounded; completely fused with clypeal wing and supraantennal plate, all reflexed margined, clypeus flattened, separated from elongated convex supraantennal plate by parallel running deep and wide clypeal furrows, slightly diverging posteriorly, extending up to a quarter of anterior eyelevel; supraantennal plate extended up to mid-eye level, clypeus separated from frons by a distinct transverse line of partly fused punctures and obtuse flat furrow, furrow turning posteriorly in form of an acute letter V, with a longitudinal pore on the frons at the bottom of the V. Frons moderately convex, with wide frontal furrow, with distinct lateral carina separating frontal furrow from supraorbital furrow, frontal furrow and lateral carina wide, distinctly diverging and extending up to neck constriction. Clypeal, frontal, and supraorbital furrows not connected. Clypeus, clypeal wing, and frons with distinct isodiametric reticulation, supraantennal plate smooth, with small depression posteriorly. Neck at middle deeper than frons, constriction developed as distinct step. Eye laterally distinctly projecting. Gena indistinct. Antenna reaching up to base of pronotum, antennomeres four to ten elongate (around twice as long as wide). Labrum distinctly convex anteriorly, reticulated, seven setose.

Pronotum: Disk in lateral view moderately convex, convex in frontal view but slightly flattened at median line. Outline oblongo-trapezoid. Reflexed lateral margin smooth, straight to slightly convex attenuated in anterior half, widest at posterior third; anterior angle not projecting; posterior angle developed as distinct obtuse tooth, tooth laterally much less projecting than widest part of lateral margin. Lateral channel as wide as reflexed lateral margin, anterior setigerous puncture located directly beside the channel, posterior setigerous puncture situated in the channel close to the tooth of the posterior angle. Median line moderately narrow; anterior transverse line slightly wider than median line, joining with median line. Surface with isodiametric to slightly transverse reticulation, with longitudinal paramedian and paralateral band of punctures; basal constriction distinct, flange more than three times wider than constriction.

Elytron: Disk flattened in anterior half in lateral view, convex on frontal view. Around 1.7 times as long as wide, lateral margin nearly parallel at middle, maximum width at middle. Reflexed lateral margin crenulated. Scutellar striole short, indistinct. Base of elytron with setigerous tubercle at base of first stria, with a small tubercle at base of third interval. Striae moderately deep, crenulatestriate, four to seven reaching base, the seventh at level of the humerus, humerus marked by distinct tooth. Stria one running to apex, two ending free at apex, three and four joining, five, six, and seven ending free apically. Intervals moderately convex, eighths slightly carinate apically. Third interval with three setigerous punctures, first distinctly removed from base and approaching third stria, the second and third approaching second stria. All intervals longitudinally reticulated, reticulation more intensive laterally.

Hind wings: Fully developed.

Lower surface: Proepisternum covered with isodiametric reticulation and few transverse wrinkles. Sternites of abdomen slightly transversely sulcate, with transverse reticulation.

Legs: Profemur dorsally sulcate. Protibia sulcate, covered with longitudinal reticulation, with three slender spines of moderate length, movable spur regularly arcuate.

Male genitalia ( Fig. 20 View Figs 14-20 ): Median lobe in ventral view distinctly and regularly curved in basal half, elongated in apical third, apex conspicuously securiform, in lateral view slightly widened at middle, apex developed as asymmetric slightly distorted wide hatchet, broadly rounded at tip of apex; endophallus with a longitudinal group and three small groups of bristles; parameres asetose.

Female genitalia ( Fig. 27 View Figs 21-27 ): Coxostylus one and two partly fused; coxostylus two gently curved at apex, ventromedially distinctly narrowed and with conspicuously wide and moderately long nematiform seta, apically with small cone-like seta, with thirteen long and one short nematiform setae; coxostylus one with two long nematiform apical setae, ventromedially with five moderately long setae, with six shorter setae at middle; laterotergite with three long, and two short setae, and with one long seta situated basally.

Variability: On the head, the V-shaped transverse line between the clypeus and frons shows more or less fewer punctures and is more or less impressed. On the pronotum the paramedian and paralateral band punctures varies regarding the number of punctures and the bands can be more or less wide and more or less extended nearly up to the anterior margin. The crenulation at the lateral margin of the elytron shows variability in their distinctness.

Distribution: Known from two locations in the Indonesian part of Borneo.

Specimens incertae sedis: MNHN; 2 specimens, labels with identical handwriting in black ink: Sumatra Palembang. One with additional label “ Syleter sumatraensis ” .

Remark: Both specimens are incomplete and in bad condition with broken elytra and missing abdomen. One is obviously a female due to some remains in the hind body. S. sumatraensis is not a valid name. – MFNB; 1 ♀, with labels and data: S.O. Borneo Grabowsky, Zool. Mus. Berlin. This incomplete specimen is close to S. sinepunctatus but might represent a new species.