Introduction to Scarab Beetles

There are more species of beetles in the world than any other group of insects and they come in all sizes, colours and shapes. Among the largest are the rhinoceros beetles, so named because the males generally have prominent horns on the front end of the body. They belong to a big family of beetles known as scarabs characterized by having antennae terminating in a club which can open out into a fan. Scarab larvae are fat, C-shaped and live in soil, dung, and decomposing plant material including wood. Other familiar scarab beetles include dung beetles, cane beetles (which damage the roots. of sugar cane) and the beautiful, iridescent Christmas beetles.

Common Rhinoceros Beetle

One of the most spectacular beetles in Australia is the Rhinoceros Beetle (Xylotrupes ulysses). It occurs from South East Asia through the islands of Indonesia to the Solomons and Australia. It is often found in Queensland’s coastal towns, including Brisbane. This black beetle reaches 60 mm in length and the male is easily recognised by its large horns; one on the top of the head and the other projecting forward from the middle of the thorax. Each hornis slightly forked at the end. The two horns almost meet, and by moving its head, the beetle can pinch weakly with them.

As well as their fearsome appearance, Xylotrupes beetles can make loud hissing squeaks when threatened. They are really quite harmless, and can be handled with safety although the claws on the ends of the legs can grip clothing or skin strongly. The hissing squeak is merely bluff and is produced by rubbing the abdomen against the ends of the wing covers; if a squeaking beetle is examined closely, the abdomen can be seen moving in time with the squeaks. These bulky beetles have large wings neatly folded under the wing covers and can fly strongly. They are attracted to lights at night and are generally noticed when they come to house lights and accumulate in large numbers beneath street lights. In Brisbane they are only seen in the summer months, but in the tropical north they can be found at any time of the year.

Only the males have horns and the females are plain black beetles. Females give off a sex hormone (pheromone) which attracts and excites males. In the presence of  females, males use their horns in combat as they try to push one another off a branch. This behaviour is the basis for a gambling game in the villages of northern Thailand where rhinoceros beetles are common. Big males are kept as pets in hollowed-out sugar cane stalks where they have both protection and food. Each male beetle is tethered to its home by a silk thread so it can fly and maintain its fitness. The males are induced to fight by putting them on the outside of a bamboo cylinder containing female beetles. The male that manages to push the other one off the bamboo is the winner.

reference: queensland museum learning

Biology

The adult beetle stage of Xylotrupes feeds on the soft bark of young shoots of many trees, a favorite being the Poinciana trees gracing so many of Queensland’s gardens and streets. Sometimes a particular Poinciana tree will become especially attractive to the beetles and large groups of them may be seen festooning its young branches. Minor damage may be caused by the feeding beetles, but it is rare for any permanent damage to occur. It is thought that these gatherings are part of the beetles’ mating behaviour.

As with all beetles, the rhinoceros beetle larvae (grubs) hatch from eggs and develop into pupae, and these eventually emerge as adult beetles. Each female lays about 50 white eggs in decaying vegetable matter and these take about three weeks to hatch. The larvae feed on decomposing vegetable material and are valuable in accelerating its break-down into compost. In New Guinea the larvae reach maturity in about eight months, but in southern Queensland, it is thought that they require two years of growth before reaching full size. The larvae of Xylotrupes are easily recognised by their translucent grey colour, fine reddish down, dark brown head and enormous size - almost filling the palm of a hand. The larvae are most commonly encountered when digging up old compost heaps or tending a well-mulched garden. In the bush, they are abundant in Australian Brush-turkey (Alectura lathami) mounds.

it with faeces that solidify into a waterproof layer. The larva then transforms into a pupa inside the cell. After about a month the adult beetle hatches out and digs its way to the surface. The beetles live for about 2-4 months.

Description and Ecology

They are among the largest of beetles, reaching more than 150 mm (6 in) in length, but are completely harmless to humans because they cannot bite or sting. Some species, such as the Hercules Beetle, have been known 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 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 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 lay 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 rather well-protected, and 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.

http://en.wikipedia.org/wiki/Dynastinae

Origin of the Rhinoceros Beetle

Dynastinae or rhinoceros beetles are a subfamily of the scarab beetle family (Scarabaeidae). Other common names – some for particular groups of rhinoceros beetles – are for example Hercules beetles, unicorn beetles or horn beetles. Over 300 species of rhinoceros beetles are known.

Many rhinoceros beetles are well known for their unique 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).

http://en.wikipedia.org/wiki/Dynastinae