Chaloenus Westwood 1861: 216

Reid, C. A. M. & Beatson, M., 2013, Chrysomelid males with enlarged mandibles: three new species and a review of occurrence in the family (Coleoptera: Chrysomelidae), Zootaxa 3619 (1), pp. 79-100 : 80-81

Chaloenus Westwood 1861: 216

Type species: Chaloenus latifrons Westwood , by subsequent designation ( Wilcox 1973)

Diagnostic description (based on Takizawa, 2012, and examination of 12 species). Small to medium sized alticine, length 3–8mm; head deflected at antennal insertions, especially in males, with genae and clypeus elongated; genae long, 0.5–2.0x eye length; male frontoclypeus without pits, setose foveae, tubercles or spines; postantennal calli well-defined, adjacent, convex, triangular to rectangular; antennal insertions close, separated by less than socket diameter; first antennomere greatly elongated, much longer than eye, second short, third elongated; labrum with truncate or convex apical margin; apical maxillary palpomere conical, shorter and narrower than preapical; pronotum strongly transverse, width 1.5– 2 x length, broadest at anterior half (usually at anterior angles); pronotum with or without discal depressions (not sharply defined); anterior pronotal border usually absent; procoxae strongly protruding, adjacent; prosternal process narrow but present between coxae; procoxal cavities closed by insertion of hypomera into apex of prosternal process; elytra non-striate to striate, rarely partially costate; elytra glabrous or with scattered erect setae; epipleuron broad at base (0.15– 2 x elytral width), gradually narrowed, upper and lower margins fusing well before elytral apex; mesoventrite process almost triangular, with truncate apex; metaventrite without posterior lobes between hind coxae; metafemur 1.5– 2 x width mesofemur, with internal folded extensor endosclerite for jumping; tibiae rarely sharply ridged externally, without apical spurs; length of first metatarsomere slightly shorter to slightly longer than 2+3; third tarsomere deeply bilobed; tarsal claws appendiculate with basal lobe large and acute; ventrites not laterally ridged; male last ventrite trilobate, with two slots defining median apical lobe; female last ventrite simple; penis elongate-cylindrical with expanded basal foramen, apex symmetrical.

Notes. The original paper erecting Chaloenus was published in issue ‘IV’ of the Journal of Entomology, dated December, 1861 ( Westwood 1861). The statement that Medvedev “erroneously dated it as 1861” ( Konstantinov & Prathapan 2008: 391) is therefore incorrect. Furthermore, the genus was originally credited with two species, both new, one described by Westwood and one by Baly. A type species was not clearly designated and the genus was not monotypic, therefore the statement by Wilcox (1973: 656), that C. latifrons Westwood is the type species by monotypy, was erroneous. Ironically, Wilcox's statement constitutes a type species designation in itself (International Code of Zoological Nomenclature 1999, Art. 69.1.1), which is C. latifrons Westwood , by subsequent designation of Wilcox. This was overlooked by Konstantinov & Prathapan (2008), who uneccessarily made the same designation.

Konstantinov & Prathapan (2008) synonymised Priostomus Jacoby, 1884 , with Chaloenus . The genus Chaloenus has recently been revised ( Takizawa 2012) with these two concepts, Chaloenus and Priostomus , retained as subgenera, separated primarily by antennal proportions.

Chaloenus is one of many genera of the leaf beetle subfamily Galerucinae with greatest diversity on the Sunda Shelf of south-east Asia. There are 42 described species ( Takizawa 2012), 36 of which are recorded from Borneo. The new species described below is also Bornean and belongs to the nominate subgenus.