scarab beetle or scarab, name for members of a large family of heavy-bodied, oval beetles (the Scarabaeidae), with about 30,000 species distributed throughout most of the world and over 1,200 in North America. North American scarab beetles range in length from less than 1/2 in. to more than 2 in. (5–50 mm); members of some tropical species grow several inches long. Many scarab beetles are brightly colored and many are iridescent.
A large group of scarab beetles are scavengers, feeding on decaying vegetation or on the dung of grazing animals. Most of these lay their eggs in underground chambers supplied with dung, where the larvae feed and pupate, emerging as adults. These scarabs, called dung beetles, play an extremely important role in the rapid recycling of organic matter and the disposal of disease-breeding wastes. Australia, which has few native dung beetle species, has imported African species to help dispose of cattle dung.
Some of the dung beetles, known as tumblebugs, form balls of dung that they roll about with their hind legs, sometimes for long distances and sometimes working in pairs. Eventually they bury the ball and lay eggs in it. One such ball-roller is the sacred scarab (Scarabaeus sacer), a black scarab beetle of the Mediterranean region. In ancient Egypt the periodic appearance of this beetle in great numbers on the surface of the Nile mud led men to associate the sacred scarab with resurrection and immortality. It was believed that all scarabs were males capable of reproducing their kind. Their ball-rolling activities were associated with the diurnal movement of the sun.
Other species of scarab beetles feed on living plants. Members of these groups include such major crop and garden pests as the Japanese beetle, the rose chafer, and the June beetle (also called June bug and May beetle). Cockchafers are Old World species similar to June beetles. Adult plant-eating scarab beetles attack leaves, flowers, and fruits, while the larvae, which develop from eggs laid in the ground, attack roots.
The largest scarab beetles in North America are the plant-eating Hercules beetles and their close relatives, the rhinoceros beetles and elephant beetles. In most species of this group the males are prominently horned. The Hercules beetles of the S United States may grow 21/2 in. (6.4 cm) long; their tropical relatives may attain a length of 6 in. (15 cm) including the horns. Despite their ferocious appearance these beetles are harmless to people.
The term scarab is also applied to representations of scarab beetles made of stone, metal, or other materials. Finely carved scarabs were used as seals in ancient Egypt; inscribed scarabs were issued to commemorate important events or buried with mummies. Roman soldiers wore scarab rings as military symbols.
Scarab beetles are classified in the phylum Arthropoda, class Insecta, order Coleoptera, family Scarabaeidae.