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 (this page), it also contains the fighting beetles.
Adults. Chafer adults usually have the final segment of their abdomen just visible from above. They have the characteristic lamellate club antennae formed by the last 3 - 7 segments of the antennae this can be clearly seen in the photograph below. Usually the adults have short, strong legs with spines, useful for digging. their bodies are usually quite stout and heavy.
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. The larvae feed on their surroundings. And they are always the characteristic "C" shape, and are usually white or grey with a hard head and three pairs of longish legs. Larval life tends to be measured in years - much longer than adult life. Melolontha melolontha, above and below, takes about two and half years to mature.
Melolontha melolontha are found in Europe and temperate areas in Asia. 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 drawings 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.
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 above 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.
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. When the adult beetle emerges it flies to trees, and for the next few days it will eat leaves and mate. Then the female returns close to where she emerged from the pupa, and lays her eggs 15 - 25 cm below the soil. She lays 25 - 40 eggs. Then she returns to the trees to feed and mate for another 2 - 3 weeks before a second period of egg laying. And this is repeated for a third session of egg laying.
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 larvae pupate over winter in soil which has a lot of decomposing vegetable matter. Adults emerge when the temperature is above 15oC.
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.
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.
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.