Arixyleborus crassior, Smith & Beaver & Cognato, 2020

Smith, Sarah M., Beaver, Roger A. & Cognato, Anthony I., 2020, A monograph of the Xyleborini (Coleoptera, Curculionidae, Scolytinae) of the Indochinese Peninsula (except Malaysia) and China, ZooKeys 983, pp. 1-442 : 1

Arixyleborus crassior sp. nov. Fig. 25A, B, I

Type material.

Holotype, female, India: Arunachal Pradesh, Etalin vicinity, 28°36'56"N, 95°53'21"E, 700 m, 12-25.v.2012, L. Dembický (ZFMK).

Diagnosis.

2.0 mm long (n = 1); 2.5 × as long as wide. This species is distinguished by the protibiae posterior faces inflated, granulate; antennal club wider than long; pronotum lateral margin oblique; pronotum anterior margin without serrations; posterolateral carina acute, granulate.

It can be further distinguished from the closely related A. silvanus by the more stout form (2.6-2.7 × as long as wide in A. silvanus ), more elongate pronotum (1.3 × longer than wide vs. 1.1-1.2 × in A. silvanus ), the more finely granulate interstriae, moderately impressed striae at the apex of the elytral disc, and the presence of short coarse setae on the declivity rather than fine hair-like setae. It can be further distinguished from the closely related A. mediosectus by the more stout form (2.86-3.33 × as long as wide in mediosectus ) and short coarse setae on the declivity.

Similar species.

Arixyleborus mediosectus , A. phiaoacensis , A. silvanus .

Description

(female). 2.0 mm (n = 1); 2.5 × as long as wide. Body uniformly dark red-brown. Legs and antennae yellow-brown. Head: epistoma entire, transverse, lined with a row of hair-like setae. Frons slightly convex from epistoma to upper level of eyes; surface alutaceous, shiny, sparsely 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. Scape regularly thick, shorter than club. Pedicle as long as funicle. Antennal funicle 4-segmented, segment 1 shorter than pedicel. Club wider than long and asymmetrical, club type 1; obliquely truncate, segment 2 not visible on posterior face; segment 1 covering posterior face, its margin completely costate; segment 2 narrow, pubescent with corneous part, visible on anterior face only. Pronotum: 1.15 × as long as wide. In dorsal view long and rounded frontally, type 7, sides parallel in basal 3/4, rounded anteriorly; anterior margin without serrations. In lateral view elongate with disc much longer than anterior slope, type 8, summit low. Surface shagreened, anterior 1/2 finely asperate; asperities close, arranged in concentric rings from midpoint of pronotum to anterior margin; anterolateral areas unarmed; disc minutely and sparsely punctate; glabrous. Lateral margins obliquely costate. Base weakly bisinuate; setal tuft absent. Elytra: 1.5 × as long as wide, 1.24 × longer than pronotum. Scutellum moderately sized, linguiform, flush with elytra, flat. Elytral base weakly bisinuate, edge oblique, humeral angles rounded; sides straight from base to apical 1/2 of declivity then rounded to apex. Disc longer than declivity, distinctly separated; interstriae shiny, minutely, finely uniseriate punctate from base to midpoint, sparsely setose, nearly glabrous, basal 1/2 shagreened, dull, becoming sharply carinate and tuberculate; striae impressed on basal 1/2, strial punctures larger, shallower than on apical 1/2, interstriae laterally diverging from base to declivity and narrowed on declivity. Declivity obliquely truncate, densely shagreened, dull, sculpturing consisting of much weaker interstrial carinae and impressed striae; striae punctate, punctures large, shallow; interstriae tuberculate, tubercles small, each bearing a short, recumbent seta, less than the distance between tubercles in length, interstriae 1 strongly inflated on apical 1/2, interstriae 1-3 carinae extending to apex of declivity. Posterolateral margin carinate to interstriae 7. Legs: protibiae slender, slightly broadened distally; posterior face inflated, tuberculate; outer margin of apical 1/2 with six small socketed denticles. Meso- and metatibiae flattened, outer margin evenly rounded, eight and ten socketed denticles on outer margin, respectively; posterior face unarmed.

Etymology.

L. crassior = stouter, comparative form of crassus (stout). An adjective.

Distribution.

India (Arunachal Pradesh).

Host plants.

The species has only been recorded from Castanopsis ( Fagaceae ).

Remarks.

The holotype is card mounted. Characters on the ventral surface including the submentum, prosternal posterocoxal piece, and denticles on the outer margins of the tibia were unable to be viewed. Socketed denticles are present on all tibiae.

Figures

Figure 25. Dorsal, lateral and declivital view of Arixyleborus crassior holotype, 2.0 mm (A, B, I), A. grandis, 3.2 - 3.5 mm (C, D, J), A. granifer, 2.8 - 3.0 mm (E, F, K), and A. granulifer, 1.9 - 2.0 mm (G, H, L).