Tricosa, Cognato & Smith & Beaver, 2020

Cognato, Anthony I., Smith, Sarah M. & Beaver, Roger A., 2020, Two new genera of Oriental xyleborine ambrosia beetles (Coleoptera, Curculionidae: Scolytinae), Zootaxa 4722 (6), pp. 540-554 : 547-548

Tricosa , gen. n.

( Figs 19–38 )

Type species. Tricosa metacuneola ( Eggers, 1940) . Description. Female. Length 2.20–3.80 mm and 2.50–3.00 times as long as wide. Body sparsely to densely setose; color light brown to ferruginous. Appearing moderately slender, elytra attenuate. Mycangial tufts absent.

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, fine, shallow, punctures larger, deeper on frons. Eyes weakly emarginated above level of antennal insertion, upper portion of eyes smaller than lower part. Submentum slightly impressed below genae, narrowly triangular. Scape regularly thick, shorter than club. Antennal funicle four-segmented, segments equal in size. Pedicle shorter than funicle. Club flattened, approximately circular; segment 1 corneous, transverse on anterior face, nearly covering all of posterior face; segment 2 slightly procurved, corneous, always visible on both sides (type 3, Hulcr et al. 2007).

Pronotum. 1.05–1.25 times as long as wide. Pronotum from lateral view with disc as long or shorter than anterior slope (type 7, Hulcr et al. 2007). In dorsal view, elongate, parallel-sided, anterior margin rounded (type 7; Hulcr et al. 2007), with or without a row of serrations. Surface alutaceous, anterior half asperate, asperities close, arranged in concentric arcs from midpoint of pronotum to anterior and anterolateral areas; disc finely and evenly punctate. Lateral margins rounded without carina. Base transverse.

Elytra. 1.26–2.0 times as long as wide. Elytral bases transverse, margins oblique; humeral angles rounded. Scutellum small, triangular, flat, flush with elytra. Sides straight from base to apical half of declivity; attenuate at apical third, apex attenuate and rounded. Interstriae parallel along their length. Disc longer than declivity. Disc smooth, shining, finely punctate; discal interstriae punctures seriate or confused. Interstriae parallel along their length. Declivital interstriae impunctate, granulate, densely setose. Posterolateral margins rounded, costa absent.

Legs. Procoxae contiguous, prosternal posterocoxal piece conical, slightly inflated. Protibiae distinctly triangular, broadest at apical third, or obliquely triangular, posterior face flat, unarmed; 5 or 6 large denticles present on outer margin of apical third. Meso- and metatibiae obliquely triangular, flattened, posterior face unarmed.

Diagnosis. Tricosa can be distinguished from all other Xyleborini genera by the following combination of characters: antennal funicle four segmented, antennal club type 3 ( Hulcr et al. 2007) with one or two sutures visible on the posterior face, protibia distinctly or obliquely triangular with 6 or fewer denticles on outer margin and posterior face flattened and unarmed, scutellum small, flush with elytra surface, mycangial tufts absent, elytra attenuate, discal punctures seriate and posterolateral costa absent.

Tricosa resembles Cyclorhipidion , Cryptoxyleborus and Fraudatrix gen. n., with which it shares either a setose and/or an attenuate appearance. Tricosa is most similar to Cyclorhipidion and they share a setose appearance and can be distinguished from Cryptoxyleborus and Fraudatrix gen.n. by the following diagnostic characters ( Tricosa given first): protibia obliquely triangular vs semi-circular with evenly rounded outer edge; typically attenuate elytra vs rounded, truncate or excavated; outer margin of protibia with 5–6 socketed denticles vs 6–9+; anterior margin of the pronotum typically serrate vs unarmed (rarely serrate). Tricosa can be distinguished from Cryptoxyleborus by the visible scutellum, and from Fraudatrix by the four segmented antennal funicle and antennal club type 3 with one or two sutures visible on the posterior face, and the pronotal disc being as long as or shorter than the anterior slope.

Etymology. F. tricosa (L.) = trickster. In reference to its confusing similarity to Cryptoxyleborus and Cyclorhiphidion.

Figures

FIGURES 19–38. Lateral, dorsal, posterior oblique and anterior view of Tricosa cattienensis (19–22), T. indochinensis (23–26), T. jacula (27–30), T. mangoense (31–34), T. metacuneola (35–38).