Madecorphnus Paulian, 1992

Frolov, Andrey V., Montreuil, Olivier & Akhmetova, Lilia A., 2016, Review of the Madagascan Orphninae (Coleoptera: Scarabaeidae) with a revision of the genus Triodontus Westwood, Zootaxa 4207 (1), pp. 1-93 : 22-23

Genus Madecorphnus Paulian, 1992

Madecorphnus Paulian, 1992: 171 ; Frolov 2010a, 2010c.

Drepanognathus Lansberge, 1886: 92 (in part: Paulian 1977; synonym of Orphnus MacLeay : Frolov 2005). Sissantobius Ritsema, 1888: 217 (in part: Paulian 1937, 1977; synonym of Orphnus MacLeay : Frolov 2005). Type species. Drepanognathus falciger Lansberge, 1886 , designated by Paulian (1977).

Diagnosis. Madecorphnus are small-sized (4.5–7.0 mm) beetles with mostly uniform, brown to black coloration. Upper side of the body has a few setae with distinct locations: 1 seta on the elytral base near epipleuron, 1 seta on the posterior angle of the pronotum, 1 seta approximately in the middle of the lateral margin of the pronotum, 2 setae on the anterior angle of the pronotum, 2 setae on the lateral sides and 2 setae on the anterior margin of the frontoclypeus. Mandibles asymmetrical, subequal in length in females and subequal to strongly unequal in males. Frontoclypeus symmetrical to asymmetrical in males, wide, bordered anteriorly, smooth, without tubercles or ridges. Pronotum wider than long, smooth, similar in both sexes, without any depressions, tubercles, or ridges. Propleurae smooth, convex, without carinae separating anterolateral areas from basal area. Scutellum triangular, narrowly rounded apically, about 1/10 the length of the elytra. Elytra convex, with feebly marked humeral humps, smooth, with only first stria distinct. Wings fully developed. Metepisternon triangular, tapering caudally, with slightly widened anterodorsal angle slightly overlapping epypleuron. Protibiae with 3 outer teeth. Phallobase strongly sclerotized dorsally and with a thin membrane ventrally. Parameres relatively long, their apices tapering or curved downwards, without setae. Internal sac of aedeagus has species-specific armature.

Sexual dimorphism in Madecorphnus is weaker than in the other Orphninae taxa. The sexes mostly differ in the shape of the mandibles. Males with the relatively feebly-developed mandibles are similar to females. In Madecorphnus , the sexual dimorphism character common for all Orphninae genera, the absence of distinct protibial spur in males, is less expressed. Often, the apical seta is longer and more robust than the others and is similar to the spur ( Fig. 10 H). However, examination of this seta at higher magnification shows that it bears minute, feebly visible setae while the true spurs are always smooth. Madecorphnus males also lack any frontoclypeal horns and prothoracic ridges, tubercles or excavations, which are found in the majority of species of almost all genera of the Orphninae .

Diagnostic characters. The shape of the mandibles is species specific at least in some species, but it is subject to allometric variability and therefore cannot always be a reliable diagnostic character. The most useful characters to separate species proved to be the number and shape of the internal sac sclerites and the shape of the parameres.

Species composition, distribution, and habitat. Madecorphnus is endemic to Madagascar and the most speciose genus of the Madagascan Orphninae with 19 described species. The species are distributed throughout the island but mostly in its eastern part. The notable exception is M. falculoides , which was found in the western part. The majority of the localities agree well with the current distribution of the remnants of indigenous forests. Little is known about bionomy of Madecorphnus . Some specimens were collected in carrion baited pitfall traps. However, it is unknown if they were attracted to carrion or captured accidently. A few specimens were collected in flight intercept traps or sifted out of forest litter. Madecorphnus species are probably generalist saprophagous litter dwellers but the labels of most of the collected specimens lack any data about the way the beetles were collected. Nesting behavior and preimaginal stages are so far unknown.

Remarks. The first known species of the genus Madecorphnus and its type species, M. falciger ( Lansberge, 1886) , was originally described in the genus Drepanognathus Lansberge, 1886 , along with D. mandibularis Lansberge, 1886 (currently Orphnus mandibularis ). Since the generic name Drepanognathus was preoccupied, the replacement name Sissantobius Ritsema, 1888 was used for the two species. The name Madecorphnus was proposed by Paulian (1977) to accommodate M. falciger and S. falculoides Paulian from Madagascar and to separate these two species from African Sissantobius mandibularis (sensu Paulian) , the type species of the genus Sissantobius . Synonymy of the names Drepanognathus , Sissantobius , and Madecorphnus is discussed in more detail in Paulian (1992) and Frolov (2005).

Paulian (1977: 1204) illustrated the peculiar aedeagus and evaginated internal sac of M. falciger (sensu Paulian) , but these illustrations do not agree with the aedeagus of the type of M. falciger . The shape of the parameres is similar to that of M. niger Frolov, 2010 , but the internal sac with numerous short spinules having wide round bases is unknown in any described Madecorphnus species. We failed to find this specimen, apparently belonging to an undescribed species, in the collection of MNHN.

Figures

FIGURE 10. Madecorphnus montreuili. Habitus in dorsal view (A—male, C—female), aedeagus in lateral view and parameres in dorsal view (B), labels of holotype (D), internal sac of aedeagus (E—photograph, F—schematic representation of armature), distributional records (G), protibia (H, male left, female right).