Arixyleborus longicauda Sittichaya, Beaver & Smith, 2024

Sittichaya, Wisut, Beaver, Roger A. & Smith, Sarah M., 2024, Four new species of Arixyleborus Hopkins, 1915, ambrosia beetles from Thailand (Coleoptera: Curculionidae: Scolytinae: Xyleborini), Zootaxa 5446 (1), pp. 65-76 : 70-71

Arixyleborus longicauda Sittichaya, Beaver & Smith sp. nov.

http://zoobank.org/ urn:lsid:zoobank.org:act:ED529319-BF73-4948-A81D-ACE0E8D452A8

( Fig. 3 )

Type material. Holotype, female: THAILAND: Chiang Mai Province, Chiang Dao Wildlife Sanctuary , 19°21’38.5”N 98°55’12.5”E, 540m, mixed deciduous forest, ethanol baited trap, 04.vi.12, W. Sittichaya ( NHMW) ; Paratypes, same as holotype (9) (1, RABC; 1, MSUC; 1, THNHM; 6, WSTC).

Diagnosis. 1.80–1.90 mm long (mean 1.84, n = 10); 2.78–3.03× as long as wide. This species is distinguished by the pronotum type 7 in dorsal view, evenly rounded anteriorly, anterior margin without serrations; elytral disc with striae impressed and interstriae raised from basal third; disc evenly rounded into declivity, apex angularly rounded; declivital face steeply sloping, weakly convex, dull; declivital interstriae 1–4 with flattened, stout, bristle-like setae, outer interstriae with long hairlike setae; posterolateral margin costate and denticulate; protibiae with posterior surface inflated, strongly granulate. This species resembles A. rugosipes but is distinguished by ( A. longicauda given first): body color very dark brown to pitchy black vs body paler, ferruginous to brown; punctures on pronotal disc larger and deeper vs punctures minute, shallow, inconspicuous; elytra more elongate, 1.56–1.67× as long as wide vs less elongate, 1.39–1.50× as long as wide; elytral disc gradually curving into declivity vs disc angularly separated from declivity.

Description. Female. 1.80–1.90 mm long (mean 1.84, n = 10); 2.78–3.03× as long as wide. Body dark brown to pitchy black, appendages paler. Head. Epistoma entire, transverse, with a row of dense, long, hair-like setae. Frons feebly convex from epistoma to upper level of eyes; surface alutaceous, subshiny, densely finely granulate in lower half, more sparsely above; punctures minute, each with a short, fine, erect, hair-like seta. Frons without distinct medial line or if present developed on upper half of frons (3 of 10 type specimens present). Eyes emarginate above level of antennal insertion, upper portion of eyes slightly smaller than lower part. Submentum deeply impressed, very narrow, triangular. Scape thick, as long as club. Pedicel as long as funicle. Antennal funicle 4-segmented, segment 1 shorter than pedicel. Club longer than wide, type 1, obliquely truncate, segment 2 not visible on posterior face; segment 1 occupying approximately basal half, concave on anterior side, with sharp marginal costa; segment 2 narrow, pubescent with very narrow corneous part, visible on anterior face only. Pronotum. 1.24‒1.39× as long as wide. In dorsal view type 7, long and rounded frontally, sides parallel in basal 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 small, moderately deep, moderately dense punctures, each with a very short, suberect seta. Lateral margins obliquely costate. Base weakly concave. Elytra. 1.56‒1.67× as long as wide, 1.12‒1.29× longer than pronotum. Scutellum moderately sized, linguiform, slightly elevated above adjacent part of elytra. Elytral bases weakly bisinuate, edge oblique, humeral angles rounded. Sides parallel from base to apical 1/2 of declivity, then angularly rounded to apex. Disc 1.5× as long as declivity, basal 1/2 shiny, apical 1/2 matt; striae and interstriae flat in basal 1/3, densely, shallowly punctured, each puncture bearing a very fine, hairlike seta, very short on striae, longer on interstriae; apical 2/3 of disc with striae increasingly deeply impressed towards apex; interstriae raised, each with a single row of granules increasing in size posteriorly; vestiture similar to basal part with strial hairlike setae minute, and interstriae with 2 or 3 irregular rows of longer, stouter setae. Disc evenly rounded into steeply sloping declivity; declivital face feebly convex, strongly shagreened, dull; striae feebly impressed, impunctate, glabrous, wider than on disc and wider than interstriae; interstriae ridgelike, with a single row of granules, decreasing in size towards apex; interstriae 1‒4 reaching apex of declivity, bearing flattened, stout, bristle-like setae, biseriate on interstriae 1, uniseriate on interstriae 2‒4; outer interstriae abbreviated, not reaching apex, with long, hairlike 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.

Male. Unknown.

Etymology. Latin adjective, from longus = long, and cauda = tail, referring to the elongate elytra compared to related species.

Distribution. THAILAND: Chiang Mai Province.

Figures

FIGURE 3. Arixyleborus longicauda sp. nov. holotype female A) dorsal view B) lateral view C) postero-lateral view D) frons E) antenna.