Many rhinoceros beetles are well known for their bizarre shapes and large sizes. Some famous species are, for example, the Atlas beetle (Chalcosoma atlas), common rhinoceros beetle (Xylotrupes ulysses), elephant beetle (Megasoma elephas), European rhinoceros beetle (Oryctes nasicornis), Hercules beetle (Dynastes hercules), Japanese rhinoceros beetle or kabutomushi (Allomyrina dichotoma), ox beetle (Strategus aloeus) and the unicorn beetle (Dynastes tityus).
They are among the largest of beetles, reaching more than 150 mm
(5.9 in) in length, but are completely harmless to humans because they
cannot bite or sting. They have been documented to support items up to
850 times their own weight. Their common names refer to the
characteristic horns borne only by the males of most species in the
group. Each has a horn on the thorax and another horn pointing forward
from the center thorax. The horns are used in fighting other males
during mating season, and for digging.
The body of an adult rhinoceros beetle is covered by a thick exoskeleton.
A pair of thick wings lay atop another set of membranous wings
underneath, allowing the rhinoceros beetle to fly, although not very
efficiently, owing to its large size and large horns. Their best
protection from predators is their size and stature. Additionally, since they are nocturnal, they avoid many of their predators during the day. When the sun is out, they hide under logs or in vegetation to camouflage
themselves from the few predators big enough to want to eat them. If
rhinoceros beetles are disturbed, some can release very loud, hissing
squeaks. The hissing squeaks are created by rubbing their abdomens
against the ends of their wing covers. Rhinoceros beetles are rather
well-protected, and the adults usually live two to four months, and
occasionally longer.
These beetles' larval stages can be several years long. The larvae feed on rotten wood and the adults feed on nectar, plant sap and fruit. First, the larvae hatch from eggs and later develop into pupae before they reach adult status
(see picture at left). The females lay 50 eggs on average. Contrary to
what their size may imply, adult rhinoceros beetles do not eat large
amounts, unlike their larvae, which eat a significant amount of rotting
wood.
Rhinoceros beetles are popular as pets in parts of Asia, in part due to their being clean, easy to maintain and safe to handle. Also in Asia, male beetles are used for gambling fights.
Since males naturally have the tendency to fight each other for the
attention of females, they are the ones used for battle. To get the two
male beetles to lock in combat, a female beetle or a small noisemaker is
used to duplicate the female's mating call.
Entomologist Séverin Tchibozo suggests the larvae contain much more protein (40%), than chicken (20%) and beef (approximately 18%) and they could become a protein source for a large [human] population.
Some species can become major pests, e.g., in tree plantations. Usually though, beetle population densities
are not as high as in some other pest insects, and food trees which are
typically already sick or dying from some other cause are preferred.
Some species' larvae, however, will attack healthy trees or even root vegetables, and when they occur in large numbers, can cause economically significant damage. The fungus Metarhizium anisopliae is a proven biocontrol agent for beetle infestation in crops in an environment friendly way.
Dr. MinJun Kim, leading a team of engineers in National Science Foundation-funded research, examined the function and aerodynamics of the Allomyrina dichotoma beetle, with the help of researchers in Drexel University's Mechanical Engineering Department and in collaboration with Konkuk University in South Korea. Rhinoceros beetles could play a big part in the next generation of aircraft design.
