They also have a distinct metallic lustre, which is the reason behind their genus name, which derives from Greek, chalko-, and is the combining form of chalkós, meaning copper.

[2] Unlike its close relatives, C. atlas, C. chiron, and C. engganensis, C. moellenkampi has a rather restricted geographic distribution and appears to occur only on Borneo.

[1] Chalcosoma moellenkampi can reach about the same size as C. atlas, and males may measure up to 110 mm (4.3 in) from the tip of the head horn to the end of the elytra (wingcases).

The largest species in the genus is Chalcosoma chiron, where males may occasionally reach 130 mm (5.1 in).

[5] In the wild, the Chalcosoma species live in rainforests and palm plantations,[2] and males and females typically meet at feeding sites, for instance wounded trees, where the beetles drink the sap.

A male tries to pin a rival between the head horn—which it can move upwards or downwards as it raises or lowers its head—and the two pronotum horns.