Dinoxyleborus sexnotatus (Schedl) Smith, 2017

Smith, Sarah M., 2017, Dinoxyleborus Smith, a new genus of Neotropical xyleborine ambrosia beetle (Coleoptera, Curculionidae: Scolytinae), Zootaxa 4303 (1), pp. 131-139 : 136-138

Dinoxyleborus sexnotatus (Schedl) comb. nov.

(Figs 11–14)

Xyleborus sexnotatus Schedl 1970: 95 .

Premnobius sexnotatus (Schedl) : Wood & Bright 1992: 655.

Diagnosis. Dinoxyleborus sexnotatus is most closely related to D. cognatoi which both have three declivital spines that increase in size from base to apex. It can be distinguished by having three to five denticles approximately evenly spaced from base to spine 1, 1–2 denticles between spines 1 and 2 and unarmed between spines 2 and 3.

Redescription. Female. Length 3.0– 3.5 mm and 3.2–3.5 times as long as wide. Body color ferruginous apically and transitioning to dark red brown posteriorly with the elytral declivity and spines the darkest. Legs and antennae ferruginous.

PLATE 4. Dinoxyleborus sexnotatus female. Figure 11. Dorsal view. 12. Lateral view. 13. Frontal view. 14. Declivity.

Head. Epistoma entire, transverse, lined with a row of hair-like setae. Frons slightly convex from epistoma to upper level of eyes; surface shagreened, dull, punctate; punctures above epistoma small, coarse, shallow, punctures increasing in size, coarseness, and depth from epistoma to upper level of eyes. Eyes moderately emarginated above level of antennal insertion, upper portion of eyes smaller than lower part. Submentum flat, slightly impressed below genae, broadly triangular. Scape narrow, elongate, about 3/4 length of club. Antennal funicle four segmented, segments equal in size. Pedicle longer than funicle. Club approximately circular, club type 4 ( Hulcr et al. 2007), flattened, round; segments 1 and 2 strongly procurved, corneus, segment 3 slightly procurved, corneous, visible on both sides of club.

Pronotum. Pronotum prolonged posteriorly (Type 8a, Hulcr et al. 2007), 1.1 times as long as wide. Anterior margin basic, elongate, parallel-sided, rounded when viewed dorsally (Type 9, Hulcr et al. 2007), lacking a row of serrations. Surface shagreened, anterior half finely asperate, asperities close, arranged in concentric rings from midpoint of pronotum to anterior and anteriolateral areas; disc finely and evenly punctate. Lateral margins rounded, slightly carinate on basal quarter. Base transverse.

Legs. Procoxae contiguous, prosternal posterocoxal piece short, triangular. Protibia slender, broadest at apical third, posterior face inflated, tuberculate; three small denticles present on outer margin of apical third. Meso- and metatibia with evenly rounded outer margin, flattened, posterior face unarmed. Mesotibia armed with 6 socketed denticles on outer margin, metatibia armed by 8 socketed denticles on outer margin.

Elytra. 2.0–2.1 times as long as wide. Elytral base transverse with oblique edge. Scutellum small, triangular, flat, flush with elytra. Sides straight from base to apical half of declivity; apex entire. Disc as long as declivity. Disc smooth, shining, finely punctate (except interstriae 1); each interstrial puncture bearing a single erect, fine, golden, hair-like seta 1.5–3.0 times the length between punctures (may be abraded); interstriae two times width of striae; interstriae 1 impressed, impunctate, shagreened on apical half. Interstriae parallel near base and broadened towards elytral apex. Declivity deeply concave, separated from disc by large elevated sulcus bearing denticles and spines. Declivital face densely shagreened, dull, sparsely, shallowly punctate, glabrous; basal third rugose. Declivital margin armed by three blunt spines, 4–6 denticles and abundantly ornamented with long semi-recumbent setae; spines increasing in size from base to apex. Three to five denticles approximately evenly spaced from base to spine 1, two of which on interstriae 1 and two to three on interstriae 2; 1–2 denticles at midpoint between spines 1 and 2 on interstriae 4. Spine 1 originating at basal third, on interstriae 3, 1.5 times as long as basal width, apex narrowly rounded. Spine 2 closest to spine 3, originating on basal third, on interstriae 5, twice as long as basal width, apex blunt with an acute point on dorsal edge. Spine 3 at apical margin, on interstriae 7, twice as long as basal width, thick, apex narrowly rounded to blunt apex. Declivital interstriae armed with granules dorsad to the margin of the sulcate area.

Specimens examined. BRAZIL, Rondônia, 62km SW Ariquemes, Fzda. Rancho Grande, CW & LB O’Brien, ex. merc. vap. & UV light ( CASC); Mato Grosso, Vera , X.1973, M. Alvarenga (DEB).

Distribution. Brazil (Mato Grosso, Rondônia), Suriname (Para).

Comments. This species is transferred to Dinoxyleborus from Premnobius because the submentum (pregula sensu Wood) is impressed rather than flush with the gena, which places it in Xyleborini , and the species possesses all the diagnostic characters for the genus.