Sacred Scarab (Scarabaeus sacer): Dung Beetle Facts

What is a sacred scarab?

The sacred scarab belongs to the scarab family, Scarabaeidae, and to its subfamily Scarabaeinae, the “true dung beetles”. Carl Linnaeus described it in 1758, and it is the type species of the genus Scarabaeus, the reference species on which the genus name is based. The genus includes dozens of ball-rolling beetles across Africa, southern Europe and Asia.

Scientists sort dung beetles into three working groups. Rollers shape dung into a ball and move it away before burying it. Tunnelers dig straight down beneath a dung pat and drag dung into the burrow. Dwellers live and breed inside the dung itself. The sacred scarab is a classic roller, and it is the species that gave the whole group of beetles, and the Egyptian amulets, the name “scarab”.

Appearance

The sacred scarab is a robust, rounded, entirely black beetle with a slightly glossy or matte finish. Its head is flattened into a wide shovel with six blunt teeth along the front edge. The broad front legs carry four more teeth along their outer edge, so the head and forelegs together form an arc of points that looks a little like the rays of the sun. These teeth are tools for digging and for cutting and shaping dung.

Unlike most beetles, the sacred scarab has no proper feet on its front legs. The front legs end without the usual jointed tarsus and claws, an adaptation for digging that is typical of the genus. The middle and hind legs are long and have normal feet, and the hind legs are slightly curved, which helps them grip a round ball.

Males and females look almost the same. Under the hard wing cases (elytra) lie folded flight wings, so adults can fly to new dung sources.

How big is a sacred scarab?

Adults measure about 1.9–4 cm (0.7–1.6 in) long, with females and males overlapping widely in size. That makes the sacred scarab one of the larger dung beetles in Europe, though tropical relatives can be bigger. Individual size depends largely on how much food the larva had inside its brood ball.

Its dung ball is often larger than the beetle itself, and a rolling scarab can move a ball that weighs many times its own body weight.

Habitat and range

The sacred scarab lives in warm, open country around the Mediterranean and the Black Sea, across North Africa, and through western Asia east to Iran, Pakistan and Kashmir. European records come from countries such as Portugal, Spain, France (including Corsica), Italy, Greece, Bulgaria, Romania, Hungary and Ukraine.

In Europe it is mainly a coastal species. It favors loose, sandy soils where digging is easy, such as coastal dunes and the edges of coastal marshes. In the Camargue in southern France, for example, it is found almost only in dunes and marshes near the sea. Farther south and east it also lives in dry pastures, steppe and semi-desert, wherever there is a steady supply of dung from cattle, sheep, goats, horses, donkeys or camels.

Adults are active in the warm months, from spring into early autumn, and spend cold or very dry spells buried in the soil.

What does the sacred scarab eat?

The sacred scarab feeds on dung, mainly from plant-eating mammals. Dung of grazing animals still contains plenty of partly digested plant material, microbes and water, which the beetle filters and absorbs. Adults find fresh dung by smell and fly in quickly, because a fresh pat soon attracts many competing beetles.

At the dung pile, the beetle uses its toothed head and front legs to cut out a portion and pat it into a ball. It then rolls the ball away from the pile, buries it in a small underground chamber and stays there to eat it, which can take several days. When the food is gone, it comes back up and looks for more dung.

How do sacred scarabs roll dung balls?

A rolling scarab moves backward. It grips the ball with its long middle and hind legs, keeps its head down and its front legs on the ground, and pushes. This lets it move a heavy ball over sand and small obstacles. Rollers try to travel in a straight line away from the dung pile, because a beetle that circles back risks having its ball stolen by others.

Ball-rolling dung beetles steer with the sky: they use the position of the sun and the pattern of polarized light it creates, and some night-active African relatives can even orient by the Milky Way. Read more in how dung beetles navigate, and see why dung beetles roll balls for the reasons behind the behavior.

The French naturalist Jean-Henri Fabre studied the sacred scarab in Provence in the 19th century. He showed that beetles that seemed to be helping a roller were often trying to steal the ball, and he described in detail how the females build their brood balls.

Reproduction and life cycle

When a female is ready to breed, she chooses especially fine, moist dung, often from sheep, and buries it deeper than a feeding ball, in a larger chamber. Underground she sculpts it into a pear shape. In the narrow neck of the “pear” she leaves a small hollow, lays a single large egg inside it and seals it. She then leaves to repeat the process elsewhere.

The larva hatches inside the brood ball and eats the dung around it, growing through three larval stages without ever leaving its chamber. It then pupates inside the hardened shell of the ball. The pale pupa, with its legs and wings pressed against its body, looks rather like a tiny wrapped mummy. In Fabre’s observations, development from egg to adult took roughly two months in summer. The new adult breaks out of the ball and digs its way to the surface, often after autumn rain softens the soil.

Each female produces only a small number of young, around half a dozen in her life according to commonly cited estimates. This low output is balanced by heavy parental investment: every offspring starts life with a protected chamber and a full food supply.

Predators and threats

Like other large dung beetles, sacred scarabs are eaten by insect-eating birds, lizards and small mammals such as hedgehogs and foxes. Their hard body and habit of spending much time underground give them some protection. They also carry mites: one species, Macrocheles saceri, rides on the beetles to reach fresh dung.

The main pressures on the species in Europe come from changes in land use. Dung beetles depend on grazing animals, so a decline in traditional grazing removes their food. Some drugs used to treat livestock for internal parasites, such as ivermectin, pass into the dung and are known to harm dung beetle larvae and adults. Coastal development and heavy use of beaches also destroy the sandy dune habitat the sacred scarab prefers in Europe.

Conservation status

The sacred scarab has not been assessed for the IUCN Red List, so its global status is Not Evaluated. It is still common in parts of North Africa and western Asia. Around the northern edge of its range, in parts of Europe, entomologists have reported that large ball-rolling dung beetles have become scarcer, in line with the wider decline of dung beetles where grazing has stopped or livestock is routinely treated with antiparasitic drugs.

The sacred scarab in ancient Egypt

To the ancient Egyptians, the sacred scarab was the living image of Khepri, the god of the rising sun. Just as the beetle rolls its ball across the ground, Khepri was believed to push the sun across the sky each morning. The Egyptian word kheper, written with a scarab sign, meant “to come into being”, and young beetles climbing out of the earth from their buried dung balls seemed to show life arising on its own.

Scarab-shaped amulets and seals were made in huge numbers from about 2000 BC onward, and scarabs were placed with the dead as symbols of protection and rebirth. The full story, and the real biology behind it, is told in why the scarab was sacred in ancient Egypt.

Relationship with people

Today the sacred scarab is valued less as a god than as a hard-working recycler. By burying dung, scarabs and other dung beetles return nutrients to the soil, loosen and aerate it, help water soak in, and remove breeding sites for flies and parasites that would otherwise develop in dung lying on the surface. Seeds in dung can also be buried and later sprout.

The sacred scarab is harmless to people: it does not bite, sting or damage crops. For a sense of how this beetle fits into the wider insect world, see how many beetle species there are.