Beetles in the Scarabaeidae family, dung beetles, chafers, rhinoceros beetles

Scarabaeidae Family

Melolontha melolontha, cockchafer flying

Above is Melolontha melolontha, the common cockchafer or May bug. It is a member of the Scarabaeidae family. There are over 20 000 species in the world in this family, 300 in Europe, and 89 in the British Isles. They range in size from 0.2 - 17 cm.

The Scarabaeidae contain two main groups, the dung beetles and the plant-eating chafers.

Melolontha melolontha, cockchafer adult

Adults. Chafer adults usually have the final segment of their abdomen just visible from above. Both groups have the characteristic lamellate club antennae formed by the last 3 - 7 segments of the antennae this can be clearly seen in the photographs of dung beetles below. Usually the adults have short, strong legs useful for digging.

Larvae. Scarabid grubs (see the drawing below) usually develop in the soil and feed on roots (chafers), or are found in dung or decaying organic matter. And they are always the characteristic "C" shape.

Melolontha melolontha

The cockchafer female has a shorter antennae club than the male. The male's antennae end in 7 flaps that can be opened up and closed like a fan. Each flap is studded with sensory pits receptive to the chemical signal released by the female. When opened like a fan the male has a better chance at detecting the chemical molecules. When the flaps are closed it means he is not seeking a mate. The female has only 6 flaps. The elytra (wing cases) are reddish brown. Cockchafers range in size from 20 - 35 mm.

Although very large and heavy they do fly, and the drawing above show the position of the front wing cases during flight, and at rest. When they fly they make a buzzing noise which can be alarming, but they are harmless.

Their flight speed has been recorded as 3.0 metres per second with a wing beat of 46 per second. Compare this with other insects.

The adults eat flowers and foliage.

Melolontha melolontha larva, cockchafer grub

The female deposits her eggs about 15 cm below the soil surface. The larva, see above, eat plant roots, with grass roots being preferred. They feed near the surface during warm months, and become inactive during winter. The drawing on the right is of a three-year-old larva. They can grow up to 60 mm long. They have a shiny brown head and legs, with a dirty white body. The larvae are sometimes called rookworms as rooks are supposedly fond of eating them. They live on this diet for three - four years before digging a burrow and pupating in an oval cell about 60 cm deep in the soil, see below.

Melolontha melolontha, cockchafer chrysalis

Pupation takes a month, but the adult will remain in the pupation cell until spring. The adult beetles emerge from the soil around May, which is why they are also known as May bugs. They are found in Europe and temperate areas in Asia.

Cetonia aurata, rose beetle, or rose chafer

Cetonia aurata, rose beetle, Scarabaeidae

Above is Cetonia aurata it is a brilliant golden green above and coppery underneath, though the colours can vary. The elytra have irregular transverse white streaks. The larva feeds on plant roots, humus and rotten wood especially beneath elm stumps, and can be considered a pest. The larvae grow up to 50 mm long, the have a brown head and legs, and a dirty white body.

The adults fly from April until September and are commonly found in flowers where they feed on pollen. Their maxillae are modified to form pads tufts and brushes to collect the pollen. The adults are unusual in that they can fly with their elytra (wing cases) closed, unlike other beetles which have to fly with their elytra open. They range in size from 14 - 20 mm.

Goliath beetle, Goliathus orientalis

Goliath beetle, Goliathus orientalis

The Goliath beetle, above, is the heaviest beetle. Body length for males is 50 - 110 mm, and females are 50 - 80 mm. Above you can see the characteristic black and white or cream markings of the adult. The males have a relatively small Y-shaped horn which they use to fend off other males when they are competing for females to mate with. In the wild they are found in the tropical forests of Africa.

Despite its huge size this beetle is a frequent and strong flier. Adults live on tree sap and fruit. In captivity adults can live for a year. Soon after it emerges as an adult the beetle searches for a mate. The female lays her eggs, which measure 4 x 2 mm, singly underground. The eggs hatch in around 2 weeks.

Larvae live in the soil, and in captivity they are often reared on cat or dog food. When young the larvae can have cannibalistic tendencies. In good conditions they are fully grown and ready to pupate in around four months. A fully grown larva can reach 130 mm long and weigh 100 g. Pupation takes place in the soil. In the wild they usually pupate during the dry season, and emerge as an adult as the rains start.

Xylotrupes gideon, rhinoceros beetle, elephant beetle

Xylotrupes gideon, rhinoceros beetle, adult male

Above and below are a preserved specimens of an adult male elephant beetle, also known as the Rhinoceros beetle and the Siamese rhinoceros beetle. They are found in South-East Asia and Northern Australia, but now can be found in captivity worldwide as they make popular pets.

Rhinoceros beetle, Xylotrupes gideon

The adult length is very variable 35 - 70 mm, and as is common with these large-horned beetles the female is much smaller All are black or dark brown and very shiny. Only the male has the two-pronged horn on his head. He uses it to knock other males out of the way when he smells a female.

When disturbed adults can make a sound that has been described as a hiss or a squeak. This is made by rubbing the abdomen against the elytra (wing cases). After mating the female lays around 50 white eggs in decaying vegetation. These eggs hatch after around three weeks. The larvae eat decaying vegetation, and can take two years to grow to full size. The beetle pupates in a hole in the soil that it lines with faces which hardens to form a waterproof shell. Pupation takes around a month. Adults are nocturnal, and live for 2 - 4 months. As you can see from the photograph above they have fully functioning wings and they do fly. In Northern Thailand beetle fighting is a popular pastime, with bets being placed on the outcome.

Dynastes hercules, Hercules beetle

Hercules beetle, Dynastes hercules, adult

The Hercules beetle, Dynastes hercules, above, is one of the longest beetles in the world. It is one of the beetles commonly known as the Rhinoceros beetles. It is found in the South and Central American jungles where it forages on decaying fruit and plant material in the littler on the forest floor. Only the males have the enormous horns which can make up more than 50% of their entire body length. Adult males can be 170 mm long and weigh up to 85 g. The horns are used in fending off rival males. The beetle gets the name Hercules as an adult male can lift 850 times his own body weight. Although the females do not have the enormous horns, they do actually have larger bodies than the males.

The larva lives inside and eats rotting wood. The larval stage lasts around 2 years, and a fully grown larva can weigh up to 120 g. Fallen trees and rotting stumps are the main larval habitats.

Chalcosoma atlas

Chalcosoma atlas, an adult Rhinoceros beetle

Above is an adult male Chalcosoma atlas, a Rhinoceros beetle. Adult males are 60 - 130 mm long, and females 25 - 60 mm long. As with all Rhinoceros beetles the male uses his horns to fight off rivals for the female he hopes to mate with. They are native to Southern Asia, especially Malaysia. Although these beetles are popular as pets they can be aggressive if disturbed, both larvae and adults will bite.

The larvae eat rotting wood, and eat their way through stumps and fallen trunks. The adults eat fallen fruits.

Hercules beetle numbers have greatly decreased due to deforestation and pollution.

Their main predators are bats, rats, birds and small mammals.

Pachnoda marginata, sun beetle

Pachnoda marginata, sun beetle, adult

Below is the larva of of the sun beetle, and above is the adult. These are sold as pets and are quite easy to rear if kept at room temperature. The grubs are also reared to be fed to reptiles.

Pachnoda marginata grub, sun beetle

Anisoplia sp

Anisoplia, sp. adult beetle

Above is an Ansioplia sp., these are found in central Europe. Note the lamellate antennae.

The adults live mainly on cereal and grass flowers, and the larvae on grass roots. They tend to be found on warm, dry slopes with sandy soil.

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