Adiscus cyaneus Tan, 1992

Duan, Wen-Yuan & Zhou, Hong-Zhang, 2022, Revision of the genus Adiscus Gistel, 1857 (Coleoptera: Chrysomelidae, Cryptocephalinae) from mainland China, Zootaxa 5096 (1), pp. 1-80 : 29-32

Adiscus cyaneus Tan, 1992

(Figs 11-1; 11-2)

Adiscus cyaneus Tan, 1992b: 782 (type locality: Sichuan; type deposited: IZ-CAS); Medvedev, 2008: 202 (Yunnan); Schöller et al., 2010: 607 (catalogue).

Material examined. CHINA: Holotype: male, " Sichuan: Ganzi [Chinese letters] / 3650 m / Chinese Academy of Sciences [ Chinese letters] // 11. VII. 1983 / coll. Yuanqing Chen [Chinese letters] // HOLOTYPE ". ( IZ-CAS) ; Paratypes: 1 female, " Sichuan: Mt. Gongga [Gonggashan], Yanzigou [ Chinese letters] / 2350 m / Chinese Academy of Sciences [ Chinese letters] // 4. VI. 1983 / coll. Xuezhong Zhang [Chinese letters] // PARATYPE ”. ( IZ-CAS) ; 1 male, " Sichuan: Mt. Gongga [Gonggashan], Yanzigou [ Chinese letters] / 2340 m / Chinese Academy of Sciences [ Chinese letters] // 5. VI. 1983 / coll. Shuyong Wang [Chinese letters] // PARATYPE ". ( IZ-CAS) .

Redescription. Measurements. Males. BL = 2.34–2.59 mm, BW = 1.42–1.74 mm, HL = 0.75 mm, HW = 0.73 mm, PL = 0.69 mm, PW = 1.48 mm, PA = 140°, EL = 1.84 mm, EA = 160°, AL = 0.62 mm, AW = 0.19 mm.

Female. BL = 2.64–2.82 mm, BW = 1.68–1.86 mm, HL = 0.81 mm, HW = 0.79 mm, PL = 0.75 mm, PW = 1.60 mm, PA = 140°, EL = 1.99 mm, EA = 160°, SL = 0.47 mm.

Body (Figs. 11-1A; 11-2A) small, oval, dorsum smooth and shiny. Head black, apex of clypeus, labrum, and antennomeres 1–4 yellowish brown, 5–11 black. Pronotum black. Elytra dark blue. Legs mostly dark brown, femur, base and apex of tibiae, and tarsus brown. Venter piceous black.

Head sparsely and finely punctate. Eyes oblong; superior eye-lobes separated by more than antennal insertions. Clypeus with weakly transverse wrinkles, anterior margin slightly arched and emarginated.Antennae reaching to the elytral humeri, scape clubbed, pedicel spherical, about half as long as scape, antennomeres 3–5 slender, cylindrical, almost as long as pedicel, 6–11 broadened and flattened.

Pronotum (Figs. 11-1A; 11-2A) smooth, impunctate, base much broader than apex, the width of base almost 2.1 times as long as pronotal length. Anterior margin nearly straight. Basal margin sinuate with fine serration, and produced into an obtuseangle of about 140° at middle. Disc evenly convex, smooth.

Elytra (Figs. 11-1A; 11-2A) smooth, as long as wide, as broad as pronotum at base, humeri prominent. Disc with fine punctures, with 11 regular striae; nearly intervals impunctate. Epipleural lobe (Fig. 11-2B) small, lateral margins weakly expanded ventrally and finely arcuately lobe-formed at basal 1/3 of elytron, with both sides forming angle of 160°, epipleura obliquely placed and visible in lateral view.

Venter clothed with sparsely short pubescence. Prosternal episternum with weak wrinkles and short pubescence, prosternal epimeron smooth. Prosternum (Fig. 11-2C) broad, rugose, lateral margin slightly prominent, posterior margin straight. Mesoventrite slightly trapezoid, 2/5 times as long as wide, anterior margin narrower than prosternum. Pygidium with dense coarse punctures.

Aedeagus. (Figs. 11-1D–F; 11-2D–F) Median lobe elongate, 3.3 times as long as wide, parallel-sided. Apex of median lobe gradually narrower than middle, acute at apex, and bent ventrally, with short pubescence on each side of apex, impunctate. Median orifice with median sclerite bending inwards above surface. Inner sac almost spherical, with coarse point-like structure, posterior margin bilobed, a small sphere with punctures directly below this. Tegmen Y-shaped, weakly sclerotized, nearly translucent.

Female. Body more robust than male, apical hollow in ventrite 5 shallow and round. Spermatheca (Figs. 11-1C; 11-2G) falcate, 45°-angled bending halfway, acute at apex, base more wide; duct base thickened strongly, almost not coiled, then becoming thinner, and coiling about 3–4 times. Rectal sclerites (Fig. 11-1G) strongly sclerotized, two sclerites rectangular, not connected in the ventral view.

Distribution. China (Sichuan, Yunnan).

Diagnosis. This species is similar to A. glabricollis , but can be distinguished by elytral puncture rows of elytra not weakened at apex, and the color of the antennae and legs being different.