Three Horned Rhinoceros Beetle

The three-horned rhinoceros beetle, Chalcosoma moellenkampi, is a giant beetle from the rainforests of Borneo in Southeast Asia. Males carry three long horns: two curving forward from the thorax and one rising from the head. It is one of the most spectacular beetles in the world.

Three-horned rhinoceros beetle Quick Facts

Common name	Three-horned rhinoceros beetle
Scientific name	Chalcosoma moellenkampi
Kingdom	Animalia
Phylum	Arthropoda
Class	Insecta
Order	Coleoptera
Family	Scarabaeidae
Genus	Chalcosoma
Type	Insect (rhinoceros beetle)
Diet	Adults drink sap and fruit juice; larvae eat rotting wood
Habitat	Rainforests, especially hilly areas
Native range	Borneo
Size	Males up to about 10 cm; females about 4.5-6 cm
Special feature	Males have three long horns used for fighting

It belongs to the genus Chalcosoma, a small group of huge rhinoceros beetles that also includes the Atlas beetle and the Caucasus beetle. The name comes from the Greek word chalkos, meaning copper or bronze, because these beetles have a shiny, metallic gleam.

Where It Lives

Chalcosoma moellenkampi lives only on Borneo, the largest island in Asia. It is found in warm, wet rainforests, especially in hilly areas. Its relatives live elsewhere in Southeast Asia, and the Atlas beetle is also common on Borneo.

Adults are active at night. They fly through the forest looking for food and mates, and they are often attracted to bright lights.

What It Looks Like

Males are much bigger than females. A large male can measure around 10 cm from the tip of his head horn to the end of his wing covers. The Caucasus beetle, the biggest member of the group, can reach about 13 cm. Male three-horned rhinoceros beetles are a dark, glossy bronze or greenish black.

Females have no horns at all. They are about 4.5 to 6 cm long, with a duller, rougher body. The females of the different Chalcosoma species look so alike that only experts can easily tell them apart.

Big Males and Small Males

Not all males are the same size. How big a beetle becomes depends on how well it fed as a larva, because adult beetles do not grow. A well-fed larva becomes a large male with enormous horns, sometimes longer than his body. A larva that grew up with less food becomes a smaller male with short horns.

Scientists say the horns grow “out of proportion” to the body: as males get bigger, their horns get much bigger still. Even small males can mate, though, so both sizes have a part to play.

Behavior and Fighting

Males and females usually meet at feeding spots, such as trees oozing sap. Big males are very aggressive and chase smaller males away from food and females.

When two large males meet, they fight. Each one tries to grab his rival between his head horn and thorax horns, like a pair of tongs, while gripping the branch with his legs. Then he tries to lift the other beetle and throw him off the tree.

Small males usually avoid these battles. In the closely related Atlas beetle, small males sometimes sneak in to mate with a female while the big males are busy fighting. The three-horned rhinoceros beetle may do this too.

These beetles are so aggressive that they often hurt each other when kept together in captivity. For this reason, they are less popular with beetle keepers than the Atlas beetle, and less is known about how they breed.

Life Cycle

Rhinoceros beetles are a type of scarab beetle. There are well over a thousand species of rhinoceros beetles worldwide, from the tropics to North America. Their life cycles differ, but all go through four stages: egg, larva, pupa and adult.

After mating, the female lays her eggs in rotting wood or in soil rich in decaying plant matter. The eggs hatch into large, C-shaped white grubs. A grub goes through three larval stages, eating rotting wood and growing very fat.

When it is fully grown, the larva builds a big oval chamber out of soil or wood and turns into a pupa inside it. For Chalcosoma beetles, the journey from egg to adult takes over a year. Chalcosoma larvae can bite, and they will even attack each other if kept close together.

What It Eats

Adult rhinoceros beetles eat only liquid foods. In the wild, they drink tree sap and the juice of ripe or rotting fruit. Larvae do most of the eating in a beetle’s life, munching through dead wood and leaf litter.

People who keep rhinoceros beetles feed adults slices of apple or banana, or special beetle jelly. Jelly is popular because it does not attract flies the way fruit does. Larvae are kept in rotting wood and leaf mold.

Amazing Facts

• Rhinoceros beetles are some of the strongest animals for their size and can lift many times their own weight.
• Despite their fearsome horns, they cannot bite or sting people as adults, and the horns are used only for fighting other males.
• Many rhinoceros beetles can make a squeaking or hissing sound by rubbing parts of their abdomen against their wing covers.

Three-horned rhinoceros beetle FAQs