Onthobium is a genus of dung beetles in the family Scarabaeidae, subfamily Scarabaeinae. It was first described by the French entomologist Édouard Reiche in 1860, based on specimens collected by the missionary and naturalist Xavier Montrouzier in New Caledonia. The type species is Onthobium macleayi Montrouzier, 1860.
Etymology
The genus name is derived from the Greek onthos (dung) and bios (life), referring to the coprophagous (dung-feeding) lifestyle of these beetles.
Taxonomy and Classification
Onthobium is classified within the tribe Deltochilini (formerly Epilissini in some classifications) of the subfamily Scarabaeinae. The genus is part of a group of eight endemic dung beetle genera found in New Caledonia, which also includes Anonthobium, Paronthobium, Ignambia, Caeconthobium, Baloghonthobium, Falsignambia, and Pseudonthobium.
Distribution
All species of Onthobium are endemic to the archipelago of New Caledonia in the southwestern Pacific Ocean, including the main island of Grande Terre and the Loyalty Islands. They primarily inhabit forested environments on ultramafic soils, at elevations ranging from approximately 200 to 1,000 meters.
Description
Adult Onthobium beetles are small to medium-sized (approximately 5–8 mm in length), with oval to elongate, convex bodies. Their coloration is typically dark brown to bronze or black, sometimes with a metallic sheen. The head features a clypeus that may bear two or four denticles (small teeth) along the anterior margin. The antennae are lamellate, and the legs are adapted for digging, with the protibiae (foreleg tibiae) typically bearing three external teeth. Sexual dimorphism is present, with males often exhibiting more prominent cephalic projections and differences in the shape of the anterior and posterior tibiae.
Species
The genus Onthobium contains 13 recognized species (as of 2011), all endemic to New Caledonia:
- Onthobium asperatum Fauvel, 1903
- Onthobium boucheti Paulian, 1986
- Onthobium caledonicus Paulian, 1935
- Onthobium cookii Paulian, 1986
- Onthobium gutierrezi Paulian, 1984
- Onthobium howdeni Paulian, 1984
- Onthobium kuscheli Paulian, 1984
- Onthobium lerati Paulian, 1935
- Onthobium macleayi Montrouzier, 1860 (type species)
- Onthobium montheiti Paulian, 1986
- Onthobium montrouzieri Paulian, 1984
- Onthobium paniei Paulian, 1986
- Onthobium tibialoides Paulian, 1986
- Onthobium tillieri Paulian, 1986
Several species originally placed in Onthobium have since been reassigned to related genera such as Paronthobium, Anonthobium, and Pseudonthobium following taxonomic revisions.
Ecology
Onthobium species are paracoprid dung beetles, meaning they tunnel directly beneath dung pats to bury portions of the dung underground for feeding and reproduction. They play a role in nutrient cycling by incorporating organic matter into the soil. The beetles are typically found in moist leaf litter and soil layers near dung sources in humid forest environments.
References
- Paulian, R. (1986). "Onthobium nouveaux ou peu connus de Nouvelle-Calédonie [Col. Scarabaeidae Canthoninae]." Bulletin de la Société entomologique de France, 91(7-8): 229–236.
- Montreuil, O. & Théry, T. (2011). "Revision of the New Caledonian genus Pseudonthobium Paulian, 1984 (Coleoptera: Scarabaeidae: Epilissini)." Zootaxa, 2863: 49–62.
- NCBI Taxonomy Browser: Onthobium (taxonomy ID: 206715).
- IRMNG (2021). Onthobium Reiche, 1860.
