Rhinoceros beetle have black heads and olive-green to light brown forewings (elytra). This species exhibits sexual dimorphism, with males having small black spots on the elytra. Females are usually smaller than males, and lack the long horns of the male. The body of the female is covered in a layer of short, soft hairs. The spots on the elytra of females are lighter and much less distinct.
Adult beetles feed on decaying vegetable matter and tropical fruit, while larvae feed on decaying wood. In captivity, larvae are fed dog food pellets and other foods rich in proteins. It is important that larvae consume sufficient nutrients, as this affects adult size.
Dynastes hercules are nocturnal, and are strongly attracted to lights. These beetles are known to fly into campfires and upon rescue from the burning flames, fly right back in!
Rhinoceros beetles mate during the rainy season. During the mating period, males become very aggressive. Dueling males face off and make threatening head bobbing movements which produces a chirping sound. The beetles try to grasp their opponent with its horns, to lift it off its feet and fling it to the ground. Sometimes, one beetle may be cut in half by its opponent’s horns. The victorious beetle may march around the defeated opponent to celebrate its success in battle. Observing this aggressive behavior, some native South Americans consume these beetles to obtain the special power related to the beetle’s size and strength.
Female beetles lay eggs in decaying wood. The larva of D. hercules assumes a C-shaped form. The larva molts three times, with the third stage (instar) larva growing to over 120gm. During this instar the larva eats large amounts of decayed wood. The larva then forms a pupation cell using wood particles from the surrounding substrate. The larva pupates inside this structure which provides protection during this defenseless stage. Upon emergence, the adult is very fragile as its elytra have not hardened. It may take up to three weeks for the elytra to become fully sclerotized (hardened) and attain its final dark color. Body color is dependent on humidity, with beetles being lighter in drier conditions and darker when humidity is high.
Cynthia Klich
Luanna Prevost
Insect Biology & Diversity Fall 2002
