Arixyleborus perbrevis Sittichaya & Smith, 2025

Arixyleborus perbrevis Sittichaya & Smith sp. nov.

Materials

Type status: Holotype. Occurrence: recordedBy: W. Sittichaya; individualCount: 1; sex: female; lifeStage: adult; disposition: Naturhistorisches Museum Wien; occurrenceID: DD8C905C-B8BB-5E51-9052-1E6A0D802F8C; Taxon: kingdom: Animalia; phylum: Arthropoda; class: Insecta; order: Coleoptera ; family: Curculionidae ; genus: Arixyleborus ; specificEpithet: perbrevis ; taxonRank: species; nomenclaturalStatus: sp. nov; Location: locationID: Hat Yai District; continent: Asia; country: Thailand; stateProvince: Songkhla Province; county: Thailand; verbatimElevation: 120 m; verbatimLatitude: 6 ° 55 ' 20.8 "; verbatimLongitude: 100 ° 14 ' 48.8 "; Event: samplingProtocol: ex. small branch of fallen Castanopsis inermis ( Fagaceae ); eventDate: 12. viii. 2024; year: 2024; habitat: tropical rainforest

Description

(Fig. 2 View Figure 2 ) Female. 1.56 mm long (n = 1), 0.6 mm wide, 2.60 × as long as wide. Body dark brown; appendages paler. Head. Epistoma entire, sinuate, with a row of sparse, short, hair-like, greenish-gold setae. Frons feebly convex from epistoma to dorsal margin of eyes; surface alutaceous and subshiny. Lower part of frons without a distinct medial line, upper part with a short, small, subshiny medial line. Lower half of frons granulate-punctate; granules moderate in size and moderately sparse. Upper half of frons punctate without granules; punctures small and shallow, each with a greenish-gold seta (mostly abraded). Eyes emarginate above the level of antennal insertion; upper portion slightly smaller than the lower. Submentum deeply impressed, very narrow and triangular. Antennal scape thick, slightly longer than club (6 / 5.5). Pedicel as long as funicle. Antennal funicle with 4 antennomeres; antennomere 1 shorter than pedicel. Club as long as wide, type 1, obliquely truncate; club antennomere 1 occupies approximately the basal half, concave on anterior side, with a sharp marginal costa; antennomere 2 narrow, pubescent, without sclerotised part, antennomere 2 not visible on posterior face, visible only on anterior face.

Pronotum: 0.7 mm long, 0.6 mm wide, 1.17 × as long as wide. In dorsal view type 7, long and rounded anteriorly, sides parallel in posterior 2 / 3; anterior margin without serrations. In lateral view, type 8 disc much longer than anterior slope, summit low. Anterior slope finely asperate, asperities low, closely spaced, with very fine, short hair-like setae. Disc alutaceous, shiny, with fine, moderately dense punctures, some short, suberect setae present on lateral and posterior margins. Lateral margins obliquely costate. Posterior margin weakly concave. Elytra. 0.81 mm long, 0.60 mm wide, 1.35 × longer than wide, 1.16 × longer than pronotum. Scutellar shield moderately sized, subrectangular, slightly elevated above adjacent part of elytra. Elytral bases weakly bisinuate, edge oblique, elytral area adjacent to scutellar shield weakly impressed, humeral angles rounded. Sides parallel from base to apical 1 / 2 of declivity, then rounded to apex. Disc 1.3 × as long as declivity, anterior 1 / 3 shiny, posterior 2 / 3 dull; striae and interstriae flat in anterior 1 / 4, densely and shallowly punctured, each puncture bearing a very fine, hair-like seta, very short on striae, longer on interstriae (almost abraded in holotype); posterior 3 / 4 of disc with striae increasingly deeply impressed towards apex; interstriae raised, each with a single row of irregularly placed granules increasing in size posteriorly to declivital summit; striae 2‒3 × narrower than interstriae; vestiture with minute strial hair-like setae and interstriae with 2 or 3 irregular rows of longer, stouter setae (almost abraded in holotype). Declivity abruptly rounded, very steep; declivital face distinctly convex, strongly shagreened, dull; striae feebly impressed, impunctate, wider than on disc and slightly wider than interstriae; interstriae feebly elevated, distinctly lower than that on disc, without granules, decreasing in size towards apex; interstriae 1‒4 reaching apex of declivity, bearing flattened, stout, bristle-like setae (almost abraded in holotype); outer interstriae abbreviated, not reaching apex, with long, hair-like setae as on disc. Posterolateral margin of elytra costate, denticulate, to interstriae 7. Legs. Protibiae slender, widest in apical 1 / 4; posterior face inflated, strongly granulate; outer margin with five distinctly separated, socketed denticles in apical half. Meso- and metatibiae flattened, outer margin evenly rounded with eight socketed denticles; posterior face unarmed.

Diagnosis

1.56 mm long (n = 1), 0.6 mm wide, 2.60 × as long as wide. This species is distinguished by combination of the following characters: pronotum type 7 in dorsal view, elongate and rounded anteriorly; type 8 in lateral view with a low summit and a distinctly longer disc than the anterior slope; elytral disc 1.3 × as long as the declivity; elytral striae and interstriae flat in the anterior quarter; elytral interstriae raised and irregularly granulate apically, with granules increasing in size posteriorly; declivity abruptly steep, rounded, strongly shagreened, convex; declivital interstriae elevated lower than that on disc, without granules, striae impunctate without vestiture.

This species resembles A. rugosipes , but can be distinguished as follows (with A. perbrevis characters given first): smaller body size, 1.56 mm long vs. larger, 1.7–2.0 mm; body shorter, 2.60 × as long as wide vs. more elongate, 2.83–3.33 × as long as wide; declivity abruptly rounded and very steep vs. gradually descending.

The generic placement of Arixyleborus perbrevis was determined in accordance with the outline proposed by Smith et al. (2020).

Etymology

Latin adjective, perbrevis = short, referred to its short elytra compared to related species.

Distribution

THAILAND: Songkhla Province (recorded only from holotype).

Biology

This species was found breeding in a small branch of Castanopsis inermis .