Arixyleborus nudulus Smith, Rabaglia, and Cognato, 2018

Zavedeev, E. V., Jäggi, B., Zürcher, Josef, Neuenschwander, Beat, Zilova, O. S., Shupegin, M. L., Presniakov, M. Yu. & Pimenov, S. M., 2018, Effects of AFM tip wear on frictional images of laser-patterned diamond-like nanocomposite films, The Coleopterists Bulletin 72 (4), pp. 838-844 : 841-843

Arixyleborus nudulus Smith, Rabaglia, and Cognato , new species

( Figs. 1–4 ) Zoobank.org/ urn:lsid:zoobank.org:act:89C5BF3C-00E4-445D-A63E-C2A66AC3EFFE

Type Material. Holotype female: VIETNAM: Dong Nai prov., Cat Tien NP, 11.42232°, 107.42834°, 128 m, 25.ii.2017, VN103, AI Cognato, TA Hoang, ex. 1–3 cm dia branch ( NMNH) . Paratype females: VIETNAM: Dong Nai prov., Cat Tien NP, 11.42232°, 107.42834°, 128 m, 25.ii.2017, VN103, AI Cognato, TA Hoang, ex. 1-3 cm dia branch ( MSUC, 3). VIETNAM: Hoa Binh prov., Luong Son district , 20°52 ʹ 14 ʹʹ N, 105°30 ʹ 00 ʹʹ E, 13.xii.2016, sample E7-4, Pham Quang Thu, ex. trap with 95% ethanol ( NMNH, 1) .

Diagnosis. Length 1.50—1.80 mm (mean = 1.56 mm; n = 5); 2.5—3.0 times as long as wide. This species can be distinguished from other species of Arixyleborus Hopkins by the nearly glabrous appearance; lack of a posterolateral declivital costa; antennal club broader than tall, smooth, shiny; elytral disc as long as the declivity; unique declivital sculpturing of the interstriae with denticles (near base and more prominent laterally) or granules (near apex and more prominent medially) dorsad each puncture; and punctures large, coarse, each bearing a short, stout, semi-erect seta.

Description. Female. Length 1.50—1.80 mm (mean = 1.56 mm; n = 5); 2.5—3.0 times as long as wide. Body color uniformly ferruginous to dark brown. Legs and antennae yellow-brown. Head: Epistoma entire, transverse, lined with row of hairlike setae. Frons slightly convex from epistoma to upper level of eyes; surface shagreened, dull, punctate; punctures above epistoma large, coarse, shallow, punctures decreasing in size, coarseness, and depth from epistoma to upper level of eyes. Eyes deeply emarginated above level of antennal insertion, upper portion of eyes smaller than lower part. Submentum flat, deeply impressed below genae, very narrow, triangular. Scape distinctly thick, about 3/4 length of club. Antennal funicle 4- segmented, segments equal in size. Pedicle as long as funicle. Club broader than tall, asymmetrical, type 2 (Hulcr et al. 2007), obliquely truncate, segment 2 not visible on posterior face; segment 1 covering most of posterior face, its margin completely costate; segment 2 narrow, pubescent with corneous part, visible on anterior face only. Pronotum: 1.27 times as long as wide. Pronotum elongated, with low summit in lateral view (type 7, Hulcr et al. 2007). Anterior margin elongate, parallel-sided, rounded in dorsal view (type 7, Hulcr et al. 2007), lacking row of serrations. Surface shiny, anterior half finely asperate, asperities close, arranged in concentric rings from midpoint of pronotum to anterior margin; anterolateral areas unarmed; disc finely and evenly punctate. Lateral margins obliquely costate. Base transverse; setal tuft absent. Legs: Procoxae contiguous, prosternal posterocoxal piece short, conical. Protibia slender, broadest at apical third, posterior face inflated, tuberculate; 6 small socketed denticles present on outer margin of apical half. Meso- and metatibiae with evenly rounded outer margins, flattened, posterior faces unarmed, seven socketed denticles present on outer margin. Elytra: Elytral base transverse, humeral angles rounded. Scutellum moderately sized, ‘u’ shaped, flat, flush with elytra. Sides straight from base to apical half of declivity; lateral profile of declivity convex; apex entire, slightly acuminate. Disc as long as declivity, distinctly separated. Disc smooth, shiny, nearly glabrous, finely, sparsely punctate; each interstrial puncture bearing a single erect, fine, golden, hairlike seta equal in length to the distance between strial 842 punctures (setae may be abraded); interstriae equal to width of striae. Interstriae parallel near base and narrowed towards elytral apex. Declivital sculpture consisting of carinate interstriae and impressed striae. Declivital face densely shagreened, dull; striae impunctate; interstriae with denticles (near base and more prominent laterally) or granules (near apex and more prominent medially) dorsad each puncture, punctures large, coarse, each bearing a short, stout, semi-erect seta. Posterolateral declivital costa absent.

Etymology. Nudulus (Latin) = naked (diminutive). This species is named for its small size and distinctively naked appearance, an unusual characteristic among Arixyleborus species.

Distribution. Vietnam (Dong Nai, Hoa Binh).

Comments. This species is very similar in form to Arixyleborus mediosectus (Eggers) .

Figures

Figs. 1―4. Arixyleborus nudulus, holotype, female. 1) Dorsal habitus; 2) Lateral habitus; 3) Head; 4) Elytral declivity.