Genus Orphnus Macleay, 1819
Type species: Scarabaeus bicolor Fabricius, 1801, by monotypy.
Small to rather large beetles (body length 5–25 mm). Color uniformly brown to black. Clypeus of males of most species with more or less pronounced horn having, in case of full development in some species, a species-specific shape. Shape of pronotum varies from simply convex to having 2 more or less developed longitudinal ridges and an excavation between the ridges. Similar to clypeal horns, pronotal ridges are subject to both interspecific and intraspecific allometric variability which can only be assessed if large series of beetles are examined. Elytra convex, without ridges, more or less densely punctate with rounded punctures. In some species punctures mark elytral stria on disc, but most species have only 1st (sutural) stria distinct. Anterior tibiae normally with 3 strong outer teeth. Lateral margin basad of outer teeth not crenulated. Middle and posterior legs similar in shape; posterior femora and tibiae about 1/8 longer than middle ones. Parameres of many species are simple, flattened and tapering apically, with 1 lateral tooth near apex of each paramere. In many species the paramere shape reasonably deviates from this common type and is species-specific.
Females differ from males in having a spur on protibia and, in majority of species, in pronotum without ridges and excavation and clypeus without horn.
Species composition. The most speciose Orphninae genus currently comprising 100 nominal species. Paulian (1948) proposed a number of subgenera and species groups which, however, require reconsideration as they are largely based on the secondary sexual characters.
Distribution. The genus has a disjunctive range: six species are known from Southern and South-Eastern Asia, and the majority of Orphnus are distributed in Afrotropics. Some species have very small ranges or known from single localities which may, however, indicate undersampling rather than local endemicity.
Benderitter, E. (1912) Description d'un Ochodaeus et de deux Orphnus nouveaux. Bulletin de la Société entomologique de France., 244.
Benderitter, E. (1913a) Description de deux Ochodaeus et de deux Orphnus nouveaux d'Afrique. Bulletin de la Société entomologique de France., 359-360.
Benderitter, E. (1913b) Étude sur le genre Orphnus et descriptions de deux Orphnus et d'un Phaeochrous nouveaus (Col. Scarabaeidae). Bulletin de la Société entomologique de France, 82-85.
Frolov, A. V. (2005) Taxonomic position of Sissantobius mandibularis (Lansberge) and synonymy of Orphnus over Sissantobius (Coleoptera, Scarabaeidae, Orphninae). Journal of Afrotropical Zoology, 2, 69-72.
Gomes Alves, M.-L. (1957) Um novo Orphnus de Angola (col. Scarabaeidae). Garcia de Orta, 5, 85-87.
Paulian, R. (1948) Revision des Orphnus Africains (Coleoptera, Scarabaeidae). Annales de la Societe entomologique de France, 117, 1-75.
Petrovitz, R. (1971) Beitrag zur Kenntnis der Gattung Orphnus M'Leay (Orphninae, Scarabaeidae, Coleoptera). Revue de Zoologie et Botanique Africaine, 84, 1-46.