Chrysomelid males with enlarged mandibles: three new species and a review of occurrence in the family (Coleoptera: Chrysomelidae).

Three new species of Chrysomelidae with extraordinary extensions of the male mandibles are described: Scaphodius drehu sp. nov. and S. ferox sp. nov. (Cryptocephalinae), from New Caledonia, and Chaloenus gajah sp. nov. (Galerucinae), from Borneo. Designation of the type species of Chaloenus Westwood, 1861, is clarified. Synonymy of Scaphodius Chapuis, 1874, with Nyetra Baly, 1877, is supported. Four species of Ditropidus Erichson, 1842, described from New Caledonia, but hitherto regarded as nomina nuda, are shown to be available and are placed in Scaphodius: S. aeneus (Fauvel, 1907), comb. nov., S. nitidus (Fauvel, 1907) comb. nov., S. striolatus (Fauvel, 1907) comb. nov., S. sulcatus (Fauvel, 1907) comb. nov. Ditropidus opacicollis Fauvel, 1907, is also transferred to Scaphodius, as S. opacicollis (Fauvel) comb. nov. The genus Ditropidus does not occur on New Caledonia. Male mandible enlargment in the Chrysomelidae is reviewed: it is common in Cryptocephalinae, but otherwise restricted to a few species of Chrysomelinae, Eumolpinae and Galerucinae. Possible reasons for its distribution in the Chrysomelidae are discussed.