Luokeng Town ambrosia beetle (Xylosandrus luokengensis) and Nanling ambrosia beetle (Xylosandrus nanlingensis)

NEWS - Two new species of beetles, Luokeng Town ambrosia beetle (Xylosandrus luokengensis Lin & Gao sp. nov.) and Nanling ambrosia beetle (Xylosandrus nanlingensis Lin & Gao sp. nov.) from Guangdong, South China and Xylosandrus trunculus Park & Smith 2020 are reported from China for the first time.

Xylosandrus Reitter 1913 (Coleoptera: Curculionidae: Scolytinae: Xyleborini) is a large genus of ambrosia beetles with a wide distribution mainly in tropical and temperate regions. The genus was established together with Xyleborus morigerus Blandford as monotypic. Many species have been described or transferred to Xylosandrus. Twenty-one species have been recorded in mainland China, including two new species.

X. luokengensis can be distinguished from the Chinese Xylosandrus by the combination of its moderate size (3.0–3.1mm); by the declivital face steep, abruptly separated from disc, elytra obliquely truncate; by the posterolateral margin forming a circumdeclivital costa, costa granulate and setose; declivital face feebly convex, strongly shagreened, alutaceous and dull; by the four apparent striae present (striae 5 short, converging with striae 4 forming a loop), and by the declivital interstriae with 3–4 confused rows of punctures.

This species is similar to X. jaintianus and X. subsimiliformis but differs by the declivital interstriae. X. luokengensis has the declivital interstriae punctured, with 3–4 confused rows of punctures (vs. the declivital interstriae granulate, granulate multiseriate and confused).

The specific name refers to the locality where the specimen was collected. Chinese common name: 罗坑足距小蠹. Females were 3.0–3.1 mm long (mean = 3.05 mm; n = 5); 2.04× as long as wide. Head, antennae, pronotum, elytral disc and legs light brown, declivital face dark brown.

Head: epistoma entire, transverse, with a row of hair-like setae. Fronts weakly convex to upper level of eyes; median carina present; surface shagreened, impunctate, alutaceous, asperate; asperities longitudinal, larger, denser above epistoma, decreasing in density and height dorsally, becoming more weakly raised and sparse by upper level of eyes.

Eyes deeply emarginate just above antennal insertion, upper part smaller than lower part. Submentum narrow, triangular, moderately impressed, with several long setae. Antennal scape regularly thick, approximately as long as club. Pedicel slightly wider than scape, much 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: 0.92× as long as wide. In dorsal view rounded, type 1, sides parallel in basal 1/2, rounded anteriorly; anterior margin with a row of 10–12 small serrations. In lateral view taller (type 2), summit at basal 1/4. Slope with densely spaced, moderate asperities, covered with moderately long, fine, erect hair-like setae.

Disc shagreened, alutaceous, with very dense, fine punctures and long, fine, erect hair-like setae. Lateral margins obliquely costate. Base transverse, posterior angles broadly rounded. Mycangial tuft present along base, tuft broad, dense, laterally extending to striae 3, almost covering the entire disc.

Elytra: 1.19× as long as wide, 1.27× as long as pronotum. Scutellum moderately sized, triangular, flush with elytra, flat, shiny. Elytral base transverse, edge oblique, humeral angles rounded, parallel-sided in basal 5/6, then sharply angulate to apex.

Disc shiny, striae not impressed, punctures small, slightly shallow, punctures separated by 1–2 diameters of a puncture, moderately setose, setae erect, hair-like; interstriae flat, inconspicuously distinguishable with striae, finely punctate, punctures 2/3 size of strial punctures, strongly confused; interstriae 4–6 times as wide as adjacent striae, bearing 3 or 4 rows of confused punctures.

Declivity obliquely truncate, face feebly convex, strongly shagreened, alutaceous, dull; four apparent striae present (striae 5 short, converging with striae 4 forming a loop), striae weakly impressed, strial punctures small, moderately deep, as large as on disc, punctures subcontiguous to spaced by 0.5–1 diameter of a puncture, each puncture bearing a recumbent hair-like seta; interstriae with 3–4 confused rows of punctures, interstrial punctures fine, slightly shallow, dense, confused, setose, each puncture bearing a recumbent hair-like seta, the setae on interstriae 1 obliquely point outward, the setae on interstriae 2–5 points to apical 3/10 of suture. Posterolateral margin forming a circumdeclivital costa, costa granulate, setose, setae medium sized, erect, fine, hair-like.

Legs: procoxae widely separated; flat prosternal coxal piece. Protibiae distinctly triangular, broadest at apical 1/4; posterior face smooth; apical 1/3 of outer margin with four large socketed denticles, their length as long as basal width; apical mucro prominent, strongly incurved. Meso- and metatibiae flattened; outer margins evenly rounded with 11 or 12 small socketed denticles.

Male 2.6 mm long (n =1); 2.03× as long as wide. Body light brown. Head: not visible in dorsal view; epistoma entire, transverse, with a row of hair-like setae. Fronts weakly convex to upper level of eyes; median carina absent. Eyes much smaller than women. Antennae similar to female.

Pronotum: 1.1× as long as wide. In dorsal view subquadrate, anterior elongate. Slope with densely spaced, small asperities, bearing long, fine, erect hair-like setae. Disc flat, bearing long, fine, semi-erect hair-like setae. Lateral margins obliquely costate. Base transverse, posterior angles broadly rounded. Mycangial tuft absent.

Elytra: 1.08× as long as wide, 1.17× as long as pronotum. Triangular scutellum. Elytral base transverse, humeral angles rounded, parallel-sided in basal 5/7, then sharply angulate to apex.

Disc shiny, striae not impressed, punctures small, slightly shallow, punctures separated by 1–2 diameters of a puncture, moderately set, setae semi-erect, hair-like; interstriae flat, finely punctate. Declivity similar to female, except declivital posterolateral costa extending to interstriae 7. Legs: similar to female, Meso- and metatibiae outer margins evenly rounded with 11 small socketed denticles.

X. nanlingensis an be distinguished from the Chinese Xylosandrus by the combination of the size (1.75mm); by the elytra obliquely truncate; by the posterolateral margin forming a circumdeclivital costa and costa granulate; by the declivital face strongly shagreened; by the declivital striae and interstriae granulate, four granulate striae present, granules finely reticulate; by the summit of pronotum at basal 4/7; and by the mycangial tuft narrow, laterally extending to striae 2, longitudinally extending to basal 1/3.

Species it is very similar to X. trunculus but differs in having the base of the pronotum intact, without the medial triangular emargination and the mycangial tuft with hair-like setae in X. nanlingensis (vs. with the medial triangular emargination and the mycangial tuft with a few long scale-like setae), costa declivities without emargination (vs. with emargination at the sutures at the top of the declivities), granules of the interstriae of declivities are similar to those of striae of declivities (vs. much smaller than those of striae of declivities).

This species is also similar to X. amputatus but differs in size, 1.75 mm in X. nanlingensis (vs. 2.8 mm), declivital granulate striae in X. nanlingensis (vs. declivital punctate striae).

The specific name refers to the location where the specimen was collected. Chinese common name: 南岭足距小蠹. Females are 1.75mm long (n = 1); 2.73× as long as wide. Head, antennae, pronotum, and legs light brown, elytral disc and declivital face dark brown.

Head: epistoma entire, transverse, with a row of hair-like setae. Fronts weakly convex to upper level of eyes; median carina absent; surface alutaceous, impunctate, bearing long, erect, hair-like setae. Eyes shallowly emarginate just above antennal insertion, upper part smaller than lower part.

Submentum narrow, triangular, slightly impressed. Antennal scape regularly thick, shorter than club. Pedicel narrower than scape, shorter than funicle. Funicle 4-segmented, segment 1 much shorter than pedicel. Club approximately as long as wide, obliquely truncate, type 1; segment1 corneous, encircling anterior face; segment 2 narrow, concave, corneous on anterior face only; sutures absent on posterior face.

Pronotum: 0.96× as long as wide. In dorsal view basic and parallel-sided, type 2, sides parallel in basal 2/3, rounded anteriorly; anterior margin with a row of ten small serrations. In lateral view disc as long or slightly longer than anterior slope, type 7, disc flat, summit at basal 4/7.

Anterior slope with densely spaced, moderate asperities, becoming lower and more strongly transverse towards summit, bearing moderate, semi-erect, hair-like setae. Disc shiny, alutaceous, with sparse, fine punctures. Lateral margins obliquely costate. Base transverse, posterior angles broadly rounded. Mycangial tuft present along base, tuft narrow, laterally extending to striae 2, longitudinally extending to basal 1/3.

Elytra: 1.73× as long as wide, 1.8× as long as pronotum. Scutellum moderately sized, subtriangular, flush with elytra, flat, shiny. Elytral base transverse, edge oblique, humeral angles rounded, parallel-sided in basal 4/5, then sharply angulate to apex.

Disc shiny, striae not impressed, punctures moderate, shallow, punctures separated by 1–3 diameters of a puncture, each puncture bearing a fine, short, semi-erect hair-like seta; interstriae flat, finely uniseriate punctate, punctures 1/2 size of strial punctures, each puncture bearing a fine, short, semi-erect hair-like seta, interstriae 2–3 times as wide as adjacent striae.

Declivity obliquely truncate, face convex, impunctate, finely reticulate, strongly shagreen, bearing short, semi-recumbent, hair-like setae, denser near suture; striae and interstriae inconspicuously distinguishable, punctures replaced by granules, granules vary in size; four granulate striae present, granules finely reticulate, small and variably sized. Posterolateral margin forming a circumdeclivital costa, costa granulate, setose, setae medium sized, erect, fine, hair-like.

Legs: procoxae moderately separated; flat prosternal coxal piece. Protibiae triangular, broadest at apical 1/3; posterior face smooth; apical 1/3 of outer margin with four socketed denticles, their length longer than basal width. Meso- and metatibiae flattened; outer margins evenly rounded with eight socketed denticles.

Original research

Wei Lin, Yong-Lin Liao, You Li, Sarah M. Smith, Ya-Li Yu & Lei Gao (2024). New species and new records of Xylosandrus Reitter, 1913 (Coleoptera: Curculionidae: Scolytinae: Xyleborini) from China. Zootaxa 5528 (1): 633–647, DOI:10.11646/zootaxa.5528.1.41

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