Cercyon (Cercyon) flavimarginatus, Ryndevich & Jia & Fikáček, 2017

Ryndevich, Sergey K., Jia, Fenglong & Fikáček, Martin, 2017, A review of the Asian species of the Cercyon unipunctatus group (Coleoptera: Hydrophilidae: Sphaeridiinae), Acta Entomologica Musei Nationalis Pragae (Acta. Ent. Mus. Natl. Pragae) 57 (2), pp. 535-576 : 543-545

Cercyon (Cercyon) flavimarginatus sp. nov.

( Figs 3 , 13 )

Type locality. China, Yunnan prov., 25 km E of Zhongdian , 3300-4000 m [GPS ca. 27.82°N 99.71°E].

Type material. HOLOTYPE: ♂ ( NHMB): ‘Yunnan 1995, 25 km E of Zhongdian, 3300-4000 m., Bolm lgt., 12-14 Jul.’. PARATYPES: CHINA: YUNNAN: 63 spec. ( NHMB, NMPC, CSR, SYSU, BMNH, KMNH):same data as the holotype; 1 spec. ( NHMB): Yulong Mt. , 3200 m, 27º01N 100º12E, 24–26.v. 1993, Bolm leg.

Diagnosis. Head black; pronotum black with narrowly yellowish lateral margins; elytra yellowish with dark sutural interval, epipleura yellowish; maxillary palpi yellow; dorsal surface without hairs; elytral intervals flat; mesoventral plate narrowly elongate, ca. 6.1–7.1× as long as wide; metaventrite without femoral lines; fifth abdominal ventrite of male with emarginate area of stronger cuticle apically; sternite 9 membranous near apex, base rounded; paramere narrow throughout, almost straight on outer margin, narrowly rounded apically, apex with setae; median lobe widest near base, narrowing apically, lateral margins bearing very short setae in apical half, apex pointed, gonopore small, subapical.

Description. Form and color. Body elongate oval ( Fig. 3A ), length 2.4–3.0 mm, width 1.4–1.9 mm. Head black with very small yellowish preocular spots. Pronotum black with lateral margins narrowly yellowish, pale coloration irregularly delimited, anterior margin very narrowly yellowish. Scutellum black. Elytra yellowish to reddish-yellow, sutural interval completely or almost completely dark; epipleuron yellow or reddish-yellow. Antennae yellow except for darker club. Maxillary palpomeres yellow. Ventral surface dark brown to black, mesoventral plate and metaventral pentagon brown to dark brown, posterior margins of abdominal ventrites brownish. Legs reddish-yellow to brownish-yellow, femora brown to dark brown.

Head. Clypeus with densely arranged, moderately coarse punctures, interstices without microsculpture. Anterior margin of clypeus with narrow bead. Frontoclypeal suture undetectable. Frons without microsculpture on interstices. Eyes small, somewhat protruding, interocular distance ca. 6× the width of one eye in dorsal view. Mentum glabrous, ca. 1.5× as wide as long, densely and coarsely punctate. Antennae with 9 antennomeres, scapus ca. 1.4× as long as antennomeres 2–5 combined, club compact. Maxillary palpomere 2 strongly swollen, palpomere 4 almost symmetrical, equal to palpomere 3 in length.

Thorax. Elytra and pronotum without hairs. Pronotum ca. 2.2–2.3× as wide as long. Pronotal punctation similar to that on head. Lateral margins of pronotum with narrow bead, the bead not overlapping anterior and posterior corners, anterior and posterior margin without bead. Mesoventral plate narrowly elongate, 6.1–7.1× as long as wide, widest in medial part ( Fig. 3F ). Metaventrite with raised glabrous sparsely punctate median pentagonal area; femoral lines absent. Elytra with 10 punctate striae, striae 1–9 slightly impressed and reaching elytral base, stria 10 very short. Elytral intervals flat. Ground punctures on intervals very fine. Humeral bulge indistinct. Epipleuron flat, horizontal. Femora with sparse and shallow punctures ventrally, with distinct tibial groove. Tarsi with densely arranged whitish setae ventrally, first metatarsomere about as long as metatarsomeres 2–3 combined.

Abdomen. Abdomen with five ventrites, first ventrite distinctly longer than other ventrites, ca. 2× as long as second ventrite, bearing distinct median longitudinal carina; fifth ventrite of male with strengthened cuticle emarginate apically.

Male genitalia ( Figs 3B–D ). Phallobase ca. 1.2× longer than parameres, asymmetrical basally. Paramere narrow throughout, gradually narrowing towards apex, almost straight on outer margin, narrowly rounded apically, apex membranous, bearing setae. Median lobe widest near base, narrowing apically, lateral margins with very short setae in apical half, apex pointed; central part of lobe bearing few very short setae; gonopore small, situated subapically. Median projection of sternite 9 membranous near apex, bearing two short subapical setae, apex pointed with two setae, base rounded, median portion shorter than lateral struts.

Variation. Some examined specimens have a very weak darker triangular spot on the elytral base and a darker ultimate palpomere.

Etymology. The name refers to the laterally yellowish pronotum; composed Latin adjective flavimarginatus (- a, - um): flavus means yellow, marginatus means “with a margin”.

Biology. Unknown.

Distribution. The species is only known from two localities in northeastern Yunnan ( China) in altitudes 3200–4000 m a.s.l.

Figures

Fig. 3. Cercyon flavimarginatus sp. nov.A – dorsal and lateral habitus of the paratype from China:Yunnan:Zhondian; B–D – male genitalia of the holotype (B – tegmen; C – median lobe; D – sternite 9). E–H – ventral morphology (E – meso- and metaventrite; F – detail of mesoventral plate; G – mentum; H – prosternum and antennal groove).

Fig. 13. Known distribution of the species of C. unipunctatus species group in Asia.