Adiscus nigricollis ( Gressitt, 1942 )

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 : 56-58

Adiscus nigricollis ( Gressitt, 1942)

(Figs 23-1; 23-2)

Dioryctus nigricollis Gressitt, 1942: 334 (type locality: Sichuan, Mt. Omei ; type deposited: ICRI).

Adiscus nigricollis: Gressitt & Kimoto, 1961: 119 ; Schöller et al., 2010: 608 (catalogue).

Material examined. CHINA: Sichuan Province: 10 males, 8 females, Wenchuan, Wolong , 920 m, 23. VII. 1983, coll. Shuyong Wang ( IZ-CAS) ; 2 males, 2 females, Wenchuan, Wolong , 2100 m, 24. VII. 1983, coll. Shuyong Wang ; 4 males, 1 female, Wenchuan, Wolong , 2100 m, 24. VII. 1983, coll. Xuezhong Zhang ( IZ-CAS) ; 3 males, Wenchuan, Wolong , 1600 m, 26. VII. 1983, coll. Shuyong Wang ( IZ-CAS) ; 3 males, 4 females, Wenchuan, Wolong , 2000 m, 30. VII. 1983, coll. Shuyong Wang ( IZ-CAS) ; 1 male, 1 female, Wenchuan, Wolong , 1920 m, 26. VII. 1983, coll. Chunlai Zhu ( IZ-CAS) ; 2 females, Luding, Moxi , 1500 m, 14. IX. 1982, Shuyong Wang ( IZ-CAS) ; 1 male, Luding, Moxi, Hailuogou , 1420 m, 18. IX. 1982, Shuyong Wang ( IZ-CAS) .

Redescription. Measurements. Males. BL = 2.34–2.84 mm, BW = 1.68–1.98 mm, HL = 0.74 mm, HW = 0.79 mm, PL = 0.70 mm, PW = 1.66 mm, PA = 95°, EL = 2.23 mm, EA = 120°, AL = 0.89 mm, AW = 0.30 mm.

Females. BL = 2.54–2.86 mm, BW = 1.68–1.99 mm, HL = 0.74 mm, HW = 0.79 mm, PL = 0.70 mm, PW = 1.66 mm, PA = 95°, EL = 2.23 mm, EA = 120°, SL = 0.54 mm.

Body (Figs. 23-1A; 23-2A) short ovate, strongly convex, mostly reddish-brown. Head pitchy reddish; antennomeres 1–5 yellowish brown, 6–11 pitchy brown; apical region of mandibles black; labrum yellowish brown. Pronotum black. Elytra reddish brown or dark reddish brown. Prosternum dark yellowish brown, lateral margin black; Mesoventrite yellowish brown; Metaventrite and abdomen dark brown. Legs yellowish brown.

Head less than half as broad as pronotum, slightly convex, finely and sparsely punctate. Eyes reniform; superior eye-lobes separated by greater distance than antennal insertions. Clypeus densely granulose and sparsely punctate, anterior margin arched and emarginated apically. Frons evenly punctured. Antennae reaching elytral humeri; scape flattened, clubbed, pedicel oblong, antennomeres 3 and 4 slenderest, 3 slightly shorter than pedicel, pedicel as long as 4, 5 slightly broader, as long as 4,, 6–11 somewhat broadened and flattened, each segment about equal in length, the last segment pointed apically.

Pronotum (Figs. 23-1A; 23-2A) convex, base much broader than apex, basal width about 2.4 times pronotal length. Lateral margin feebly rounded. Anterior margin nearly straight. Posterior margin undulated, and produced into an obtuse angle of about 95° at middle. Disc smooth, with minute punctures.

Elytra (Figs. 23-1A; 23-2A) about as broad as pronotum at base, humeri somewhat prominent, feebly rounded at sides and apex. Disc convex, sparsely and finely punctate, with 11 regular striae, intervals with scattered minute punctures, puncture striae irregular on apical slope. Epipleural lobe (Fig. 23-2B) large, lateral margins distinctly expanded ventrally with rounded lobe at basal 1/3 of elytron, with both lobe sides forming angle of 120°, epipleura invisible in lateral view.

Venter clothed with finely silvery pubescence and fine punctures. Prosternum (Fig. 23-2C) trapezoidal, with obtuse angle near middle in lateral view. Mesoventrite broad, twice as wide as long. Pygidium with coarse punctures. Legs minutely punctate, first tarsomere of middle legs swollen.

Aedeagus. (Figs. 23-1D–F; 23-2D–F) Median lobe elongate, about 3.3 times as long as wide, nearly clubbed. Apex of median lobe slightly narrower than middle, apex narrowly rounded, slightly curved in lateral view; with several setae on each side of apex, densely punctate on ventral side of distal part. Median orifice with median sclerite bending inwards below surface. Inner sac rather slender, about 3 times as long as wide, cylindrical, base 1/4 broadest, then becoming narrower, apex 1/3 most narrow, bilobed and acute at apex Tegmen Y-shaped, weakly sclerotized, almost translucent.

Female. Body more robust than male, apical hollow in ventrite 5 shallow and round. Spermatheca (Figs. 23- 1C; 23-2G) falcate, 30°-angled bending halfway, acute at apex, slightly dilated at 1/3 from apex, then narrower; duct weakly sclerotized, weakly and irregularly coiling 4–6 times. Rectal sclerites (Fig. 23-1G) moderately sclerotized, not connected between two clubbed sclerites on ventral side.

Distribution. China (Sichuan).