Diuncus Hulcr & Cognato, 2009

Smith, Sarah M., Beaver, Roger A. & Cognato, Anthony I., 2020, A monograph of the Xyleborini (Coleoptera, Curculionidae, Scolytinae) of the Indochinese Peninsula (except Malaysia) and China, ZooKeys 983, pp. 1-442 : 1

Diuncus Hulcr & Cognato, 2009

Diuncus Hulcr & Cognato, 2009: 28.

Type species.

Xyleborus papatrae Schedl, 1972a; original designation.

Diagnosis.

Small to moderately sized (1.5-3.0 mm) stout species (1.33-2.78 × as long as wide). Diuncus species are distinguished by the antennal club truncate, type 1, segment 1 corneous and dominant on both sides; pronotum stout, with 4-6 serrations on anterior margin; pronotum from lateral view rounded, robust (type 5), from dorsal view rounded (type 1), rarely conical and angulate (type 6); declivity flat and broad, margins broadened and distinctly carinate, declivital base often armed with one or two pairs of denticles; protibiae obliquely triangular, with 3-5 large denticles, denticles distinctly longer than wide; scutellum visible and flush with the elytra; mycangial tufts absent; and procoxae contiguous.

Similar genera.

Ancipitis , Leptoxyleborus , Xylosandrus .

Distribution.

Found in tropical Asia and Oceania, rare in Africa.

Gallery system.

The gallery systems in Diuncus vary depending on the species and the size of the breeding material. There may be an entrance tunnel leading to a terminal brood chamber in the longitudinal plane ( D. ciliatoformis ); the gallery may branch in three dimensions and either have very irregular brood chambers ( D. mucronatus ), or lack brood chambers ( D. javanus ); in small stems, there are longitudinal branches in the center of the stem ( D. haberkorni ).

Remarks.

Diuncus species are usually mycocleptic, making use of the ambrosia fungi of other ambrosia beetles, and lack mycangia ( Hulcr and Cognato 2010b). However, some species also occur alone ( Hulcr and Cognato 2009).