Planiculus Hulcr and Cognato

Hulcr, Jiri, 2010, New genera of Palaeotropical Xyleborini (Coleoptera: Curculionidae: Scolytinae) based on congruence between morphological and molecular characters, Zootaxa 2717, pp. 1-33 : 21

Genus Planiculus Hulcr and Cognato , gen. n.

Type species. Xyleborus bicolor Blandford, 1894 .

Diagnosis. Planiculus is similar to Xyleborus and Wallacellus . It is distinguished from Xyleborus by flattened, broadened elytral declivity with very few if any tubercles, smaller size and slender body, inconspicuous prosternal posterocoxal process, elongated pronotal disc, and antennal club type 2 or 3. It is distinguished from Wallacellus spp. by much smaller size (rarely over 2.5 mm), rounded frontal margin of the pronotum, and its characteristic color pattern (basal part of pronotum often yellowish, anterior part dark yellow or brown, elytra dark brown), although variations exist.

Description. Eyes shallowly emarginate, upper portion of eyes smaller than lower part. Antennal club moreless circular shape, club type two (obliquely truncated, second segment visible on posterior side), or three (first segment straight or convex). First club segment covering most of posterior face of club, concave or straight on anterior face (may be slightly concave or convex), margin of first segment clearly costate. Second segment of club narrow, pubescent, visible on the anterior side only, or visible on both sides of club; if corneous then visible on anterior side only. Third segment of club absent from or partly visible on the posterior side of club. First segment of antennal funicle shorter than pedicel, funicle composed of 4 segments, scapus thicker and shorter than in most other genera. Mandibular mycangia may be visible as swellings on epistoma. Frons above epistoma smooth, alutaceous, with minor punctures. Submentum slightly impressed, very narrow triangle. Anterior edge of pronotum with no conspicuous row of serrations (serrations don't differ from those on the pronotal slope). Pronotum from lateral view elongated, with low summit (type 7), often with disc distinctly elongated (type 8), from dorsal view elongated basic shape with rounded frontal margin (type 7), or long, rounded anteriad (type 9). Pronotal disc shining or smoothly alutaceous, with small punctures, lateral edge of pronotum concave (pronotum very long), or obliquely costate. Procoxae contiguous, prosternal posterocoxal process conical and slightly inflated. No mycangial tufts of setae on pronotal basis or elytral basis. Scutellum flat, flush with elytra. Elytral bases straight, with oblique edge, elytral disc longer than declivity, flat, punctures in strial lines. Boundary between elytral disc and declivity distinct, or indistinct with end of disc rounded, smoothly transitioning into declivity. Lateral profile of elytral declivity gradually descending, often flat. Dorsal profile of elytral apex a useful synapomorphy: broadened laterally, sometimes narrowly emarginate. Elytral declivity with few setae or scales, not conspicuously pubescent. Posterolateral declivital costa ending in 7th interstriae. Declivital surface with no tubercles, or with uniform granules, or several tubercles on interstriae 1, 3 and beyond. First interstriae usually broadened at elytral apex, slightly inflated, bearing several tubercles. Protibiae distinctly triangular, slender on the upper part, broad and denticulate on the lower part, denticles small, their bases slightly elevated, usually 6 denticles present. Color uniformly light brown or reddish, rarely dark brown, pronotum almost always much lighter (yellow or orange) than elytra. Small to minute species, 1.4-2.5 mm, rarely up to 3.2 mm in montane species.

Etymology. L, masculine, refers to flattened elytra and small body size.

Comments. Planiculus is monophyletic in both morphological and molecular analyses (100% posterior probability, Cognato et al. 2010). Broadened declivital margin led Wood (1989) and Wood and Bright (1992) to include many Planiculus in Euwallacea . However, Euwallacea are unrelated large species ( Cognato et al. 2010) with different suite of characters ( Fig. 9 ). The lack of resolution within Planiculus on the morphology-based cladogram ( Fig. 9 ) indicates extreme similarity of several species in this group. Several such previously described species appear to be multiple re-descriptions of the same morphotype based on differences in emargination of declivital apex, and pattern of granules on declivity. Such species are synonymized here. One declivital character with phylogenetic value is whether tubercles are on interstriae 1 and 3, or on all interstriae including interstria 2. The exact position of tubercles along interstriae varies.

Figures

FIGURE 9. Morphology-based cladistic analysis of species previously placed in Euwallacea, Xyleborus, and several similar species of unclear affiliation. Combinable-component consensus of 72 MP trees, (113 steps). Numbers at nodes indicate Bremer support.