Xyleborinus tritus, 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 tritus sp. nov. Fig. 87

Type material.

Holotype: female, Vietnam: Cao Bang, 22°36.804'N, 105°51.982'E, 1831 m, 17.iv.2014, VN46, Cognato, Smith, Pham, ex punky bark (MSUC). Paratypes, female, as holotype except: 22°34.5'N, 105°52.4'E, 1080 m, 14.iv.2014, VN46, ex 8 mm twig (VNMN, 1); Lao Cai, Hoang Lien N.P., 22.35, 103.77, 1500-2000 m, 19.v.2019, VN184, S.M. Smith, A.I. Cognato, ex 6 cm trunk (MSUC, 3; NHMUK, 1); as previous except: VN191, S.M. Smith, A.I. Cognato, ex branches 1 and 7 cm (MSUC, 2; NMNH, 1).

Diagnosis.

2.2-2.5 mm long (mean = 2.33 mm; n = 4); 3.0-3.14 × as long as wide. This species is distinguished by the declivital face with interstriae 2 unarmed by tubercles, granules present on apical 1/3 of disc; odd numbered declivital interstriae strongly convex, bases of denticles tumescent; and striae 1 nearly convergent with striae 2 on declivital face, interstriae 2 not apparent.

Similar species.

Xyleborinus exiguus , X. huifenyinae , X. perpusillus .

Description

(female). 2.2-2.5 mm long (mean = 2.33 mm; n = 4); 3.0-3.14 × as long as wide. Body light to dark brown. Legs and antennae light brown. Head: epistoma entire, transverse, with a row of hair-like setae. Frons weakly convex 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 large, distinctly triangular, deeply impressed. Antennal scape regularly thick, as long as club. Pedicel as wide as scape, shorter than 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: 1.1 × 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 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: 2.1 × as long as wide, 1.9 × 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; striae not impressed, with small punctures separated by two diameters of a puncture; interstriae flat, sparsely finely uniseriate punctate, punctures 1/3 those of striae; interstriae 2 variably granulate on apical 1/3 of disc (1-3 granules present). Declivital face strongly shagreened, steeply rounded, three striae present, striae 1 and 3 convergent, interstriae 2 not apparent, strial punctures larger and shallower than on disc, glabrous; interstriae impunctate, setose, setae uniseriate and as long or longer than the width between suture and interstriae 3; odd numbered interstriae strongly convex, and denticulate, bases of tubercles tumescent; even numbered interstriae impressed; interstriae 2 impressed, unarmed along its length (granules on apical 1/3 of disc in one of two specimens examined). Posterolateral margin costate, granulate to interstriae 5. Legs: procoxae contiguous; prosternal coxal piece tall and pointed. Protibiae obliquely 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 eight and nine moderate socketed denticles, respectively.

Etymology.

L. tritus = commonplace. Named in reference to the uninteresting pattern of granules on the declivity. An adjective.

Distribution.

Vietnam.

Host plants.

Unknown.

Figures

Figure 87. Dorsal, lateral and declivital view of Xyleborinus tritus holotype, 2.2 mm (A-C).