Diuncus justus ( Schedl 1931 ) Schedl, 1931

Hulcr, Jiri & Cognato, Anthony I., 2009, Three new genera of oriental Xyleborina (Coleoptera: Curculionidae: Scolytinae), Zootaxa 2204, pp. 19-36 : 32-33

Diuncus justus ( Schedl 1931) comb. n.

Previous genus: Xyleborus

Diagnosis: Very small species, considerably variable in body proportions. The length to width ratio varies continuously from 1.5/ 0.7 mm (robust) to 2.4/1.0 mm (less robust). The holotype of Diuncus justus lies approximately in the middle of the continuum, lectotypes of the almost identical Xyleborus ciliatus , Xyleborus ciliatoformis , and Xyleborus apiculatus are more slender, but also varied (1.6/0.75; 1.7/1.1and 2.0/0.8, respectively). Synonymy of these species will be published elsewhere. The differences are attributable almost entirely to the relative length of elytral disc, whereas the shape of pronotum and the shape and slope of elytral declivity are relatively constant. Pronotum is always robust and rounded, type 5 in lateral view. Elytral color varies between black to yellow. Declivity surface is usually covered with rows of appressed setae directed backwards and towards the elytral median suture, but the pubescence is frequently absent. The most characteristic feature of the species is the complete lack of denticles on elytral declivity, and the broad and smooth depression traversing from the summit of interstria 1 to the apex in interstria 3, creating a bulge at the upper part of declivity.

Length: 1.4–2.4 mm.

Biology: Kalshoven (1960) first reported the tendency of this species to create tunnels next to entrance holes of other ambrosia beetles species. Two larger representatives of D. justus were found associated with Amasa resectus in New Guinea and in Borneo.

Examined material: Indonesia, Java, Buitenzorg, (holotype, NHMW); Malaysia, ( BMNH); Malaysia, Sabah, Danum Valley, J. Hulcr 2006; New Guinea, Morobe Province, Bulolo, ( FICB); PNG: Madang Prov. (9), Oro Prov. (1), West Sepik (1), J. Hulcr 2002–2006.