Xyleborinus disgregus, 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

Xyleborinus disgregus sp. nov. Fig. 83A, B, I

Type material.

Holotype: female, Vietnam: Cao Bang, 22°34.118'N, 105°52.537'E, 1048 m, 12-17.iv.2014, VN9, Cognato, Smith, Pham, ex FIT (MSUC). Paratypes, female, India: Arunachal Pradesh, Etalin vicinity, 28°36'56"N, 95°53'21"E, 700 m, 12-25.v.2012, L. Dembický (ZFMK, 1); Vietnam: Cao Bang, 22°33.9981'N, 105°52.591'E, 1051 m, 2-17.iv.2014, VN9, Cognato, Smith, Pham, ex FIT (MSUC, 1).

Diagnosis.

1.8-2.0 mm long (mean = 1.87 mm; n = 3); 3.0-3.33 × as long as wide. This species is distinguished by the posterior margin of elytra broadly rounded; declivital face with interstriae 1 and 2 unarmed by tubercles; declivital face feebly sulcate; small body size; lateral declivital margins weakly elevated, bearing three pairs of sharply pointed denticles, denticles increasing in size from base to apex; denticles along interstriae 5 distinctly smaller than those on interstriae 3; sulcate area impunctate, surface strongly shagreened, dull; and elongate body form.

Similar species.

Xyleborinus cuneatus , X. jianghuasuni , X. sculptilis .

Description

(female). 1.8-2.0 mm long (mean = 1.87 mm; n = 3); 3.0-3.33 × as long as wide. Body, legs and antennae light brown, elytra becoming darker apically, declivity red-brown. Head: epistoma entire, transverse, with a row of hair-like setae. Frons flattened to upper level of eyes, alutaceous, subshiny, finely, sparsely punctate, setose; punctures bearing a long, erect hair-like seta. Eyes deeply emarginate just above antennal insertion, upper part smaller than lower part. Submentum narrowly triangular, deeply impressed. Antennal scape short and thick, as long as club. Pedicel as wide as scape, as long as funicle. Funicle 4-segmented, segment 1 shorter than pedicel. Club longer than wide, obliquely truncate, type 1; segment 1 corneous, encircling anterior face; segment 2 narrow, concave, corneous on anterior face only; sutures absent on posterior face. Pronotum. 1.06 × as long as wide. In dorsal view very elongate, rounded frontally, type 9, sides parallel on basal 3/4; anterior margin without serrations. In lateral view elongate with disc much longer than anterior slope, type 8, disc flat, summit moderately prominent, at apical 1/3. Anterior slope with densely spaced narrow asperities, becoming lower and more strongly transverse towards summit, bearing long, fine, semi-recumbent hair-like setae. Disc subshiny, alutaceous, finely punctate, finely setose, setae short, erect, hair-like, some longer hair-like setae at margins. Lateral margins obliquely costate. Base transverse, posterior angles acutely rounded. Elytra: 2.0 × as long as wide, 1.88 × as long as pronotum. Scutellum minute, conical, disconnected from elytra, surrounded by dense mycangial tuft of setae. Elytral base transverse, medially emarginate near scutellum and mycangial tuft, edge oblique, humeral angles angulate, parallel-sided in basal 3/4, then broadly rounded to apex. Disc occupying basal 2/3, smooth, shiny, glabrous, unarmed; striae not impressed, with moderate punctures separated by two diameters of a puncture; interstriae flat, sparsely finely uniseriate punctate, punctures 1/3 those of striae. Declivital face strongly shagreened, dull, steeply rounded, feebly sulcate between interstriae 3; three striae present, striae and interstriae impunctate; interstriae 1 and 2 flat, unarmed on face, two small denticles present at base; interstriae 3 weakly elevated with a row of three pairs of sharply pointed denticles, denticles increasing in size from base to apex. Interstrial denticles and spines setose, setae erect, hair-like, uniseriate and as long as the width between suture and interstriae 3. Posterolateral margin without a costa, denticulate from interstriae 5-6. Legs: procoxae contiguous; prosternal coxal piece flat, inconspicuous. Protibiae distinctly triangular, broadest at apical 1/3; posterior face smooth; apical 1/3 of outer margin with six moderate socketed denticles, their length approximately as long as basal width. Meso- and metatibiae flattened; outer margin evenly rounded with 5-7 and seven or eight moderate socketed denticles, respectively.

Etymology.

L. disgregus = unlike, different. In reference to the interesting pattern of granules on the declivity. An adjective.

Distribution.

India (Arunachal Pradesh), Vietnam.

Host plants.

Unknown.

Figures

Figure 83. Dorsal, lateral and declivital view of Xyleborinus disgregus holotype, 1.8 - 2.0 mm (A, B, I), X. echinopterus holotype, 3.0 mm (C, D, J), X. ephialtodes holotype, 2.6 mm (E, F, K), and X. exiguus, 1.8 - 2.0 mm (G, H, L).