The Dynastinae are among the largest of beetles, reaching more than in length, but are completely harmless to humans because they cannot bite or sting. Some species have been anecdotally claimed to lift 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 head and another horn pointing forward from the center of the thorax. The horns are used in fighting other males during mating season, and for digging. The size of the horn is a good indicator of nutrition and physical health. The body of an adult rhinoceros beetle is covered by a thick exoskeleton. A pair of thick wings lie atop another set of membranous wings underneath, allowing the rhinoceros beetle to fly, although not very efficiently, owing to its large size. 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 relatively resilient; a healthy adult male can live up to 2–3 years. The females rarely live long after they mate. 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. 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.
Interactions with humans
Use by humans
Rhinoceros beetles have become popular pets in parts of Asia, due to being relatively 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 is used, or a small noisemaker duplicating the female's mating call. EntomologistSéverin Tchibozo suggests the larvae contain much more protein, than chicken and beef and they could become a protein source for a large human population. Dr. MinJun Kim, leading a team of engineers in National Science Foundation-funded research, examined the function and aerodynamics of Allomyrina dichotoma, 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.
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.
Tribes and Genera, with selected species
Agaocephalini Burmeister, 1847
Aegopsis
Agaocephala
Cyclocephalini Laporte, 1840
Cyclocephala
Dynastini MacLeay, 1819
Allomyrina Arrow, 1911
* Allomyrina dichotoma - Japanese rhinoceros beetle
