Wednesday, 24 September 2008

Featured Insect: Oryctes rhinoceros Linnaeus, 1758 (Coleoptera: Scarabaeidae)

The coconut palm (Cocos nucifera) is one of the quintessential plants of the South Pacific and its prominence in the lifes and history of the islanders cannot be overestimated. Coconut palms and their products, while not quite as all-encompassing as they used to be, remain a vital food source and cash crop for a large number of people around the world.

Coconuts have many enemies, one of the most serious being Oryctes rhinoceros, a large dynastine scarab beetle. Originating in South Asia, it has spread across the Pacific with the accidental assitance of man. It was first recorded from Upolu, Samoa in 1909, spread to Tonga in 1921, and was discovered on Wallis Island in 1931. World War II was instrumental to the spread of the insect to Papua New Guinea, and Fiji was invaded in 1953. Larvae grow well in a variety of organic matter including decaying vegetation, sawdust and cattle dung. The adult insects causes damage to the leaves, particularly new, actively growing axils. This damage weakens the plants and causes a loss in productivity.

Several methods have been investigated for their utility to control O. rhinoceros. Among these are the use of pathogenic fungi, and and pheromones. One of the most effective however, involves the use of a virus to infect and kill the insects. In 1963, larvae infected with a virus were discovered in Malaysia. Further investigation showed that this virus was effective for control of the beetle, and was able to be cultured in the laboratory. In 1964, the virus was released experimentally in Samoa. The virus spread quicker than expected and caused a major decline in the population of O. rhinoceros. The virus was then introduced to other countries, which also experienced the same decline. Unfortunately, it appears that the virulence of the virus has decreased. Populations are starting to increase, which is sparking further research into the virus and other control methods of the beetle.

C.C. Okaraonye and J.C. Ikewuchi have got an idea for a different biological control agent - humans. The larvae of O. rhinoceros are apparently highly nutritious and full of protein. They don't give any recipes unfortunately, but do say that they can be eaten raw, boiled, smoked or fried...

Bedford, GO. (1976.)
Observations on the biology and ecology of Oryctes rhinoceros and Scapanes australis: pests of coconut palms in Melanesia.
Journal of the Australian Entomological Society 15:241-251

Bedford, GO. (1980.)
Biology, ecology, and control of palm rhinoceros beetles.
Annual Review of Entomology 25:309-339

Huger, AM (2005.)
The Oryctes virus: Its detection, identification, and implementation in biological control of the coconut palm rhinoceros beetle, Oryctes rhinoceros (Coleoptera: Scarabaeidae)
Journal of Invertebrate Pathology 89(1):78-84

Jackson TA, Crawford AM, Glare, TR. (2005.)
Oryctes virus—Time for a new look at a useful biocontrol agent
Journal of Invertebrate Pathology 89(1): 91-94

Okaraonye CC, Ikewuchi JC (2009.)
Nutritional potential of Oryctes rhinoceros larva
Pakistan Journal of Nutrition 8(1): 35-38

Photo courtesy of Huger (2005)

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