Scaphodius Chapuis 1874: 179

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 : 83-84

Scaphodius Chapuis 1874: 179

Type species: Scaphodius comptus Chapuis 1874 , by monotypy.

Diagnostic description (based on examination of c. 50 species). Small to medium sized cryptocephalines, length 1–6mm. Head: eyes small, convex, without a distinct internal canthus; male usually with elongated or laterally enlarged mandibles; clypeal area not sharply delimited, or if so, transversely triangular with obtuse upper angle and widely splayed raised margins for holding antennae in repose; antennae not serrate, longer than head width, antennomeres 7–11 elongate and expanded, each with dense basiconic sensilla in apical circular pit. Thorax: front angles pronotum not abruptly constricted as a collar; pronotum with triangular posterior lobe, usually medially notched for retention of scutellum; hind margin pronotum with row of teeth, usually hidden by base of elytra; hind angles of pronotum posteriorly produced; prosternal process broad, sides parallel and usually ridged; scutellum abruptly raised from mesoscutum, fusiform or oval, and anteriorly stepped; mesoscutum on either side of scutellum with narrow strip of microchaetae; elytra striate; elytral suture not serrate; elytral epipleuron entirely visible in lateral view, expanded at humerus, with sinuate lower margin; tibiae without spurs; claws appendiculate. Abdomen: ventrites III, IV and V fused; penis with distinct apical setae; vaginal palpi flat, semi-ovate; spermatheca falciform; dorsal transverse sclerites of kotpresse extending beyond sides of rectum.

Notes. The genus Scaphodius is endemic to New Caledonia and was recently redescribed by Schöller (2009), with several new species. We have revised the description here, based on a larger sample of species. Schöller also included Nyetra Baly 1877 as a junior synonym of Scaphodius , with which we concur. Nyetra was described for a large species, with dorsal pubescence and extreme sexual dimorphism, in contrast to the type species of Scaphodius , small, dorsally glabrous and with slight sexual dimorphism, but there are intermediates in size and structure between these extremes, as noted by Schöller.

Schöller listed 12 species in Scaphodius but this figure excludes species wrongly placed in the Australo-Papuan genus Ditropidus Erichson, 1842 ( Schöller 2009) . Schöller treated the five species of Ditropidus described by Fauvel (1907) as either belonging to that genus ( D. opacicollis only) or nomina nuda, because they lacked detailed descriptions. However, these latter names were partially described by Fauvel (1907) as part of a key written to differentiate the species, which therefore makes them available (ICZN 1999, Art 12.1), although the species are unidentifiable from the key. Fauvel seems to have placed his species in Ditropidus based on size and colour, neither of which is valid, and faulty biogeography, influenced by Chapuis (1875a, b). Chapuis had listed D. punctulum Chapuis, 1875a , from Sydney, Adelaide and Fiji, and D. tibialis Chapuis, 1875a , from Sydney, Clarence River, Brisbane and Fiji. Chapuis also described Cryptocephalus fraterculus Chapuis, 1875b , from Fiji. All three of these species are Australian, absent from Fiji ( Bryant & Gressitt 1957; types examined by CAMR) and the specimens from Fiji examined by Chapuis must have been wrongly labelled. Note that D. punctulatus of Bryant & Gressitt (1957) is a misidentification. Fauvel was therefore misled in believing that Ditropidus occurred in “Polynesia” ( Fauvel 1907: 152).

We have examined the male holotype of D. opacicollis . This is a small but otherwise typical species of Scaphodius , with ovate eyes, laterally expanded mandibles, strongly divergent facial antennal grooves and strigose pronotum (= S. opacicollis (Fauvel) , comb. nov.). We have not seen any Ditropidus species in abundant material of Cryptocephalinae from New Caledonia. Fauvel’s generic diagnoses are clearly incorrect. We therefore feel justified in placing all of the other Fauvel names 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.

The only species of Scaphodius supposedly from outside New Caledonia, S. compactus Sharp, 1881 , was described from New Zealand. This is an Australian species of Ditropidus , either mislabelled from New Zealand or adventitive but no longer extant in that country ( Leschen & Reid 2004; Schöller 2009).

The net result of these changes is that Scaphodius is endemic to New Caledonia and Ditropidus is confined to Australia and New Guinea.

Two new species in the material available to us show particularly bizarre sexual dimorphism and are described below. This brings the total number of valid Scaphodius species to 19.