Rhinoceros Beetles: Harmless to Humans but Devastating to Some Crops
You Won't Find This Rhinoceros at the Zoo
Anyone who's ever been to a zoo has probably seen the ferocious-looking rhinoceroses. They are huge, extremely strong and have some horns the path of which you would want to avoid. This article, however, is all about an insect that has many of those same characteristics - the rhinoceros beetle.
When a rhinoceros beetle is threatened, it makes a hissing sound, but not with its mouth. Instead, the sound is made when its wings are rubbing against its abdomen. This sound might be considered a type of predator-avoidance measure for the rhinoceros beetle.
Unlike the rhinoceros, any sound this beetle makes shouldn't alarm you, unless you are another beetle. These guys are harmless to humans and they are one of only a handful of insects that make a noise loud enough for humans to hear, the loudest being a cicada.
Hercules Rhinoceros Beetles Look Ferocious
Hercules beetles, one of the more common names for the rhinoceros beetle, are large and look extremely threatening, mainly because of the huge vertically-oriented, horn-like pincers protruding from the frontal portion of the males. The horns can grow longer than the body of the beetle.
Female hercules beetles don't have horns, and the good news for us is that the male beetles use their pincers to settle disputes with other beetles. They don't use them on humans, but if you pick one up, you may be scratched by its extremely long legs (accidentally, of course).
Different species of this beetle have different looks. While they all have rounded, convex backs, their coloration varies from black to mottled greenish gray and some are shiny, almost metallic. You may even encounter one covered with short, fine hairs, giving it a velveteen appearance.
The Invasive Coconut Rhinoceros Beetle
The first official sighting of a coconut rhinoceros beetle was in Hawaii in 2013, according to the United States Department of Agriculture. The beetle is native to Asia but is considered an invasive pest in any country, as it is also known to feed on other crops besides coconuts that are economically important, such as pineapples, bananas, papayas and others.
The people of the Solomon Islands (a sovereign country of about six major islands and hundreds of smaller ones in the South Pacific) depend on coconuts both for food and for export. In 2015, the coconut rhinoceros beetle was discovered on the island of Honiara, which is the capital of the country.
In an attempt to save the valuable coconut crop, the people of Honiara carried out a delimiting survey and introduced the fungus Metarhizium anisopliae and Baculovirus oryctes, used in many countries to control coconut rhinoceros beetles, which were believed to arrived on the island from Papua, New Guinea.
In 2016, there was an outbreak of the beetles causing the island's government to declare them as "emergency pests" as about 95% of the coconut crop was lost.
The beetle attacks coconut palms by boring into the crowns or tops of the tree damaging tissue and feeding on tree sap. As a result, coconut production is significantly reduced and trees can be killed.
As late as 2017, the beetle had not only invaded Honiara, but also much of Guadalcanal and Savo Island. In January, 2018, the Government and Palm Industries Coconut Rhinoceros Beetle Task Force issued a press release entitled "Know Your Enemy" in order to educate residents about the differences between the invasive beetle and the local beetles which did not harm the valuable crops. They also advised residents to kill the rhinoceros beetle wherever it was found.
There are 400,000 species of beetles on this planet, but only 8,000 species of mammals.— John B. S. Haldane - British British Geneticist, Biometrician, Physiologist
- https://bugguide.net. Retrieved 02/20/2018
- http://www.looppng.com/global-news/coconut-rhinoceros-beetles-threaten-solomon-islands-coconut-and-palm-oil-industries. Retrieved 02/19/2018
- http://www.abc.net.au. Retrieved 02/19/2018
- Gressitt, J. L. (1953). The coconut rhinoceros beetle (Oryctes rhinoceros) with particular reference to the Palau Islands. Bernice P. Bishop Museum Bulletin 212. Honolulu, 1–83.
- Huger, A. M. (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, 78–84.
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© 2018 Mike and Dorothy McKenney