Cnestus quadrispinosus , Sittichaya, Wisut & Beaver, Roger A., 2018

Sittichaya, Wisut & Beaver, Roger A., 2018, Cnestusquadrispinosus, a new species of xyleborine ambrosia beetle from Thailand and Borneo (Coleoptera, Curculionidae, Scolytinae, Xyleborini), ZooKeys 795, pp. 31-37: 32-34

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Cnestus quadrispinosus

sp. n.

Cnestus quadrispinosus  sp. n. Figure 1A-F

Type material.

Holotype: female, THAILAND, Hala-Bala Wildlife Sanctuary, Narathiwat Province, lowland tropical rainforest, 5°47 ’44’’ N, 101°50 ’07’’ E, 01.iii.2014, ethanol baited trap (W. Sittichaya) ( NHMW). Paratypes: 12 females, same data as hol otype ( NHMW, 2; PSUZC, 2; THNHM, 2; RAB, 1; WST, 5). BRUNEI, Kuala Belalong FSC, E115°7', N4°34', Dipterocarp forest, Dryobalanops beccarii  , Aerial F[light]I[ntercept]T[rap] 3, 220m alt., 30.v.[19]91, N. Mawdsley NM 178 ( NHMUK, 1). [E. MALAYSIA], Sabah, Poring Spring, Lower montane mixed dipterocarp forest, Xanthophyllum affine  , Fog XA11/F1, 12.v.1992, A. Floren (RAB, 1).


The species is placed in Cnestus  because it possesses the following combination of characters: body rather short and stout, with very sparse vestiture; antenna with four-segmented funicle (including pedicel), club truncate and flattened, its first segment covering the whole posterior surface; anterior margin of pronotum with two large, upcurved denticles, lateral margins of pronotum carinate, disc not asperate; scutellum flush with elytral surface; procoxae narrowly separated, intercoxal process spinelike, posterocoxal process not swollen; protibiae obliquely triangular, widest about one-fourth from apex, outer margin with 6‒7 denticles in apical half, posterior face not tuberculate.

The species is distinguished from all other species of Cnestus  by the large spine on interstriae III at the upper margin of the elytral declivity, and a second large spine on interstriae V on the lateral margin of the declivity. The species belongs to a small species group which lack a mycangial tuft of hairs at the base of the pronotal disc, and in which the elytral declivity is broadly impressed. The majority of Cnestus  species have a mycangial tuft indicating the presence of a mesonotal mycangium, and a convex elytral declivity.


Female. Length 4.25 mm (paratypes 3.45-4.50 mm), 2.30 times longer than wide (paratypes 2.20-2.56 times), body stout, shining, bicoloured, head dark brown to black, pronotum dorsally entirely black, laterally brown to dark brown, at least anterior part of elytral disc yellowish brown to dusky brown, area of paler colour varying individually from a small area at base of elytra to whole disc, remainder of elytral disc and declivity dark brown to black; ventrally yellowish brown, femora pale, tibiae dark brown, antennae and tarsi brown.

Head. Frons moderately convex, shining, with an indistinct small, smooth median swelling above epistoma, and a broader slightly raised smooth area towards vertex, lower part with scattered elongate rugae, arranged subconcentrically around lower swelling, upper part with fine punctures laterally; vestiture of fine hairs of variable length, longer and denser on lower part of frons; epistoma with dense brush of stiff, yellowish setae. Eyes shallowly emarginate at antennal insertion, lower portion distinctly larger. Antenna type 1 ( Hulcr et al. 2007), scape long and slender, weakly spatulate, pedicel cup-shaped, funicle 3-segmented, the segments successively wider, antennal club large, subcircular and very flat, segment I covering posterior side, segment II corneous, visible only on anterior side.

Pronotum. Near type 7 in dorsal and lateral view ( Hulcr et al. 2007), approximately as long as wide (holotype 1:1.03; paratypes 1:0.86-1.09), basal margin raised, shallowly, broadly emarginate; sides weakly curved in basal half, widest at about middle, more strongly curved anteriorly, anterior margin projecting over head with two large upcurved asperities at apex; anterior slope convex, armed with robust, pointed asperities anteriorly, the asperities becoming more transverse, more closely spaced and lower towards summit in middle; disc weakly shining, weakly reticulate, finely punctured, the punctures more closely spaced in the Thai than in the Bornean specimens, finer and sparser posterolaterally; posterolateral margin acutely carinate from basal margin to middle of pronotum; vestiture on pronotal slope sparse, with long erect setae, disc glabrous, without mycangial tuft.

Scutellum. Small, flat, semicircular, impunctate.

Elytra. Holotype 1.13 times longer than wide (paratypes 1.05-1.33), 1.29 times longer than pronotum (paratypes 1.14-1.36), bases transverse, carinate from scutellum to humerus, a small longitudinal swelling at humerus; sides subparallel in basal two-thirds, then gradually rounded to apex; elytral disc shining, convex, striate-punctate, strial punctures fine, moderately dense, interstrial punctures uniseriate, coarser and a little more closely placed than those on striae, both sets of punctures more closely placed in Thai than in Bornean specimens, disc with a few long and fine yellowish interstrial setae; declivity commencing at about middle, steeply sloping, declivital face quite strongly, broadly, impressed, sub-shiny, the margins carinate from the apex to interstriae VII; upper margin of the declivity with a small spine on interstriae II and a much larger, posteriorly directed spine on interstriae III, another large spine of similar size on interstriae V at about mid-height of declivity, small spines or granules may also be present between these large spines on declivital margins; striae I and II impressed on the upper part of declivity, interstriae II and III much widened on declivity, almost flat, each with a row of widely separated granules or small spines bearing very long, fine hairs posteriorly.

Legs. Procoxae narrowly separated, anterocoxal process narrow, spine-like, posterocoxal process not swollen; protibia obliquely triangular, widest about one-fourth from apex, outer margin with 6‒7 denticles in apical half, posterior face weakly convex, not tuberculate. Meso- and meta-tibiae more evenly rounded with 10-11 denticles on outer margin.

Male. Unknown.


The Latin name is an adjective derived from the four (quatuor) spines (spinae) on the elytral declivity.


Brunei Darussalam, East Malaysia (Sabah), Thailand.

Host plants.