Xylosandrus derupteterminatus ( Schedl, 1951 )

Xylosandrus derupteterminatus ( Schedl, 1951) View in CoL

Fig. 2 View FIGURE 2

Xyleborus derupteterminatus Schedl, 1951: 64 View in CoL .

Xylosandrus derupteterminatus (Schedl) View in CoL : Schedl 1964: 213 s.

Material examined. 6 males: Lao P.D. R, Nam Ha National Biodiversity Conservation Area, Muang Sing, Luang Namtha province, Northern Lao P.D. R, 21.126178N, 101.243714E, 995 m alt., 14. ix. 2023, insecticide spray (B. Chouangthavy, leg; NUOL) GoogleMaps .

Male diagnosis. The male is characterized by the following combination of characteristics: frons weakly convex; eyes upper part slightly smaller or equal to lower part; anterior margin of pronotum without serrations; declivital face with large punctures, posterolateral margins of elytra costate; disc and declivity with dense hair-like setae; declivity steep, beginning at basal third, then tapering toward rounded apex; aedeagus long and slender; penis body long and narrowed towards apex ( Fig 6D View FIGURE 6 ).

Description of male. Body small, 1.1–1.5 mm long (mean = 1.3 mm; n = 6), 0.5–0.7 (mean = 0.6) time longer than wide. Pronotum, scutellum and elytra dark brown or black; antennae and legs yellowish brown to brown. Head. Epistoma undivided, transverse, with hair-like setae, with smooth surface. Frons weakly convex, weakly punctate; punctures each bearing an erect hair-like seta (0.09-0.15 mm), yellowish brown. Eyes small (approximately 0.09– 0.1 mm from upper-most to lower-most), with anterior margin weakly emarginate; upper part slightly smaller or equal in size as lower part. Submentum distinctly triangular, large, and slightly impressed. Antennal scape long and uniformly thick, slightly longer than the club (3:2); pedicel thick, as wide as the scape, varying in length, shorter than or same length as the funicle; funicle 2- to 4-segmented (4-segmented in most cases), with segments thick and short, wider than long (3:1), in individuals with 2-segmented funicles ( Fig. 4A View FIGURE 4 ), segments very flat and wider than long (4:1), in individuals with 4-segmented funicles ( Fig. 5B View FIGURE 5 ); funicle sometimes incompletely fused with the club ( Fig. 4B View FIGURE 4 ): club obliquely truncate, longer than wide as in females; segment 1 well-defined, covering the entire posterior face, with the anterior apical margin either pointed at the first club ( Fig. 5A View FIGURE 5 ) or even ( Fig. 5B View FIGURE 5 ) on anterior face. Pronotum 0.3–0.6 mm (mean = 0.45 mm), as long as wide, rounded in dorsal view (type 1 defined in Smith et al. 2020); side slightly cured forward in basal and apical thirds; pronotal disc punctate, with summit situated at middle 1/3 from base, flat and smooth. Base bears weakly defined short hair-like setae. Lateral sides of the disc short or slightly equal to the anterior slope, basic type 0, flat and slightly curved toward the summit, summit at basal 1/2; anterior margin without serrations, anterior slope weakly asperate, asperities weakly spaced, flat, lower and rare transverse toward the summit. Scutellum rounded triangular or U-shaped, moderately sized, flattened, dark brown, more visible from above. Elytra 0.5–0.9 mm (mean = 0.7 mm) as long as wide, 0.4–0.8 mm (mean = 0.5 mm), as long as pronotum, proportion of elytral length to pronotal length (0.7–0.8 mm), slightly curved at bases; humeral angles rounded; lateral sides curving from humeral angle to apex. Disc short, basal area 1/3 of disc slightly rounded, apical 3/4 humped and connecting to declivital strongly curved toward apex; surface punctate, punctures fine and setose; striae and interstriae regular punctures, becoming finer towards apex. Declivital commencing from basal third, steep; margin rounded and costate; posterolateral margin costate in apical 1/3; striae and interstriae with confused punctures? on the posterior half of elytra and declivity, each puncture becoming obsolete on declivity towards apex, bearing long fine hairs. Legs. Procoxae widely separated, interspace between procoxae 0.03 times as wide as procoxa. Protibiae obliquely triangular, with 3–5 socketed teeth on lateral margin; posterior face smooth. Meso- and metatibiae with 6–8 socketed teeth. Genitalia. Aedeagus long and slender; penis body long and narrowly to apex; apodeme slenderly curves gradually towards the apex ( Fig. 6D View FIGURE 6 )

Remarks: The antennal structure of the population of male X. derupteterminatus is extremely variable. Initially, we classified the male specimens into three distinct morphospecies based on the distinctly varied characteristics of their antennae. This variation sometimes appears even on a singleton specimen, for instance, the apical margin of the first segment of the left club is medially pointed in anterior view, while one of the right club is even ( Fig. 5 A and B View FIGURE 5 ). Additionally, in another population, the funicle segments are thick and composed of two or three distinct segments ( Fig. 4 A and B View FIGURE 4 ). The color varies from black to yellowish brown.

Distribution in Lao P.D.R: Luang Namtha province

Biological notes. We collected populations of this species from Pometia pinnata ( Sapindaceae ), found on small branches with a diameter ranging from 5 to 7 cm. These branches had fallen from a live tree, situated near a small river characterized by high humidity. The river maintained a continuous flow of water throughout the year. This primary forest habitat where samples were collected is located approximately 1 km from the main road. This ambrosia beetle species ( X. derupteterminatus ) was previously recorded only on Mangifera indica ( Anacardiaceae ) and Agathis ( Araucariaceae ) ( Smith et al. 2020).