Subfamily Orphninae (Coleoptera, Scarabaeidae)

Subfamily Orphninae

Aegidium, Madegorphnus, Chaetonyx, Pseudorphnus, males

Aegidium, Madecorphnus, Chaetonyx, Pseudorphnus, males


Subfamily Orphninae comprises small to medium-sized beetles with characters and appearance being somewhat intermediate between the two major groups of the family Scarabaeidae — dung beetles and chafers. Orphnines are uniformly colored, brown to black, without any pattern. Surface sculpture vary with majority of species having more or less densely punctate upper side of the body. Majority of genera exhibit strong sexual dimorphism with large males having variably developed clypeal horns and protoracic ridges, sometimes species-specific, but these characters are subject to allometric variability and some males of the same species are superficially similar to females.

Orphnines are a distinct, monophyletic group of scarab beetles having a number of synapomorphies, including a particular type of stridulatory apparatus, anterior coxa with a longitudinal hollow on the anterior surface, and the absence of the protibial spur in males. Some genera have peculiar characters not found in other scarabs, e.g. highly asymmetrical mandibles in Madecorphnus or lack of tarsi in Stenosternus. Flightlessness is quite common in the Orphninae and the total number of flightless species may be up to 20 per cent. Hybalus and Chaetonyx comprise completely apterous species with no visible wing rudiments whereas Stenosternus, and some Orphnus and Aegidium species have vestigial wings. Chaetonyx, a geophilous South European genus, is also almost blind with the eyes reduced to only a few facets.

Orphnines are widely distributed in tropical and subtropical regions of southern continents except for Australia, however majority of species are rare in collections and many species are known from only type specimens. Currently there are about 200 described species which are grouped into 17 nominal genera. Almost half of the species are placed in the genus Orphnus.