Oryctes

Oryctes is the economically most important genus of rhinoceros beetles in the subfamily Dynastinae (family: Scarabaeidae) and includes serious pests of palm trees. A total of 47 species have been assigned to the genus, including 2 fossil ones. The extant species are widely distributed in Africa, as well as in Europe, Asia and the Pacific. No established populations are known from the Americas. The species are typically between 30 and 60 mm long, dark brown to black, with a robust body and a strong cuticle. They can be distinguished from other genera in the tribe Oryctini by the structure of the pronotum, the horn on the head, the mouthparts and other features.

Type species: Scarabaeus nasicornis Linnaeus, 1758, a synonym of Oryctes nasicornis

Most of the extant species of Oryctes are found in Africa with only 8 species in Asia and the Pacific, 3 in the Near East and 1 in Europe. The 33 African species are mainly distributed in sub-Saharan countries, with 18 of them found in Madagascar and surrounding islands like Réunion, Mayotte, Mauritius, the Comoros and the Island of Rodrigues. Eight species (Oryctes amberiensis, O. anguliceps, O. augias, O. clypealis, O. colonicus, O. dollei, O. politus and O. ranavalo) are endemic to Madagascar and occur nowhere else.

O. nasicornis is the only European species. It is widespread in most European countries and has been also reported from some of the neighbouring regions like parts of northern Africa, the Near East and Turkey. Two species (Oryctes agamemnon and O. elegans) are common in the Near East region. A third one, Oryctes richteri, has been reported only from Iran. Oryctes rhinoceros is widespread in southern Asia and the Pacific. Other Asia/Pacific species include Oryctes ata in Turkmenistan, O. centaurus in Papua New Guinea, O. forceps in northern India ("British Bootan, Padong"), O. gnu (Malaysia, Indonesia, Thailand, the Philippines, and southern China), O. heros in Timor, O. hisamatsui in Japan, and O. nudicauda in Myanmar. No established populations are known from the Americas. Two extinct species, described from German deposits, are also sometimes assigned to Oryctes.

The species of Oryctes can be distinguished from other genera in the subfamily Dynastinae and the tribe Oryctini by a combination of different morphological features. These include:

Within a given species, there can be a considerable variation in size, length of the horn and structure of the pronotum. In some species, such variation may be due to the suitability of the breeding substrate. However, in the type species, Oryctes nasicornis, such variation is often genetic and is linked to different subspecies.

The subgenera and individual species of Oryctes are characterized, among others by:

Species of Oryctes typically breed in decaying wood like rotting tree trunks or other decaying organic matter. While a given species might have a preference for a certain type of wood, there seems to be some flexibility. Females of several species readily lay eggs in old sawdust heaps near sawmills or compost heaps in gardens. For example, decaying coconut trunks are the preferred and traditional breeding sites for Oryctes rhinoceros in Asia and decaying oak bark and wood for Oryctes nasicornis in Europe, but both species often breed in old sawdust heaps, compost heaps and other decaying organic matter. In some species, the larvae can also feed on the living tissue of tree trunks and roots. The immature stages include the egg stage, three larval stages and the pupal stage. The development from egg to adult may be completed in about half a year, but can also extend over several years.