Debus 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 : 13-14

Genus Debus Hulcr and Cognato , gen. n.

Type species. Xyleborus emarginatus Eichhoff (1878) ( Debus emarginatus (Eichhoff) : Hulcr & Cognato, this publication).

Diagnosis. Pronotal disc is elongated and flat. Tibiae are slender, triangular (not with rounded dorsal margin) with few but large and long denticles. Prosternal posterocoxal process is inflated. The main autapomorphic character is the impression and arrangement of striae on elytral declivity. Declivity is excavated and emarginate in most species (rarely flat), surrounded by an elevated sulcus, and with tubercles or teeth. The first interstriae are broadened to the extent that strial punctures are displaced laterally.

Description. Eyes shallowly emarginate, "bean shape", upper portion of eyes smaller than lower part. Antennal club more-less circular shape, club type two (obliquely truncated, second segment visible on posterior side). First segment of club circular around the club, covering most of the posterior face, margin of the first segment clearly costate all around the antenna. Second segment of club visible on both sides of club, but not corneous, or the corneous part on the anterior side only. Third segment of club partly visible on the posterior side of club. First segment of antennal funicle shorter than pedicel, funicle composed of 4 segments, scapus regularly thick. Frons above epistoma rugged, coarsely punctate. Submentum slightly impressed, shaped as distinct large triangle. Anterior edge of pronotum with no conspicuous row of serrations, only small asperities identical to those on the pronotal slope. Pronotum from lateral view 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, obliquely costate. Procoxae contiguous, prosternal posterocoxal process large and inflated. No setose tuft on pronotal or elytral basis associated with mycangium. Scutellum flat, flush with elytra. Elytral bases straight, with oblique edge. Elytral disc longer than declivity, flat, punctures on elytral disc in strial lines (may be difficult to discern). Elytral declivity not conspicuously pubescent, with few setae or scales. Details of structure of elytral declivity discussed below. Posterolateral declivital costa ending in 7th interstriae, or reaching beyond 7th interstriae and surrounding most or all of declivity. First interstriae parallel on elytral disc, but mostly broadened towards the summit of elytral disc, and distinctly broadened towards the apex of elytra. Protibiae distinctly triangular, slender on the upper part, broad and denticulate on the lower part. Posterior side of protibia flat, with setae only. Protibial denticles mostly large, distinctly longer than wide, small in small species. Bases of the denticles not enlarged to slightly enlarged, six or fewer protibial denticles present. Body length 1.8 to 4.2 mm, mostly slender species, never very robust. Color varies from light brown to black, pronotum sometimes much lighter than elytra.

Comments. The characteristic flat or excavated shape of elytra is a result of greatly broadened interstriae 1, to lesser extent also 2 and 3. Several (usually 4 pairs) large tubercles on each interstria 1, but their origin on interstria 1 is not immediately apparent. It is observable only in some species, preferably on the bottom side of elytra. The broad interstria 1 displaced most strial lines on declivity. The one dominant declivital tubercle appears to lie on or around the remnants of the first or second strial line, but it originates on interstria 1 (punctures of striae 1 and 2 are displaced, curved around the tubercle, and rarely discernible). There are usually no tubercles on striae 2 (though dominant displaced tubercle often appears as if on interstria 2), and only smaller tubercles on striae 3 and beyond, creating tuberculated elevated sulcus surrounding the declivity.

Declivital armature as a sole character for species delimitation in Debus is disputable. The elytral declivity appears to have changed extensively, while the rest of body is nearly immutable in most lineages. Especially, the relative position of the largest declivital spine, other spines, and posterolateral declivital costa was historically often used to delimit species, but these are extremely variable when a sufficient number of individuals is examined. Further, several specimens were observed with different tooth pattern on each elytron. Similarly extensive variability of declivity not corresponding with the rest of characters can be seen in Eccoptopterus .

Browne (1961) subjectively placed many Debus spp. in Coptoborus . Coptoborus was designated by Hopkins (1915) for unrelated Neotropical species. Wood (1980) expanded Coptoborus to include several Paleotropical Streptocranus spp. However, the representatives of Debus , Coptoborus and Streptocranus in the molecular phylogeny are not closely related ( Cognato et al., 2011).

Etymology. masculine; the name was inspired by Donald E. Bright, one of the major contributors to the modern classification of scolytine beetles, whose initials are printed on thousands of identification labels in the world’s bark beetle collections.

Biology. Galleries of many species contain several irregular brood chambers. Significant portion of the tunnel system is often in the phloem-xylem boundary ( Beaver & Browne, 1978).