Adult: 25 to 30 mm. Dark head, black pronotum covered in short and close-set hairs. Reddish-brown elytra each with 4 longitudinal ribs. Black abdomen, elongated and flattened pygidium. Antennae in the male longer than in the female. The last segments lamellate are more developed in the male. Larva: whitish body, curve into an arc, blackish extremity to the abdomen. Large head, bearing strong mandibles, yellow thoracic legs, elongated, slender and hairy. The grub measures 10-20 mm in autumn which follows its birth, 30-35 mm by the following autumn, and reaches its maximum size, 40-46 mm in the spring of its third year.
Biology and Damage
Adults feed on hazelnut leaves like in other forest and fruit trees. The larvae are very polyphagous. They attack the roots of various crops. Adults appear in April-May, fly singly , particularly at dusk, then migrate towards a feeding site. After 10-15 days of feeding, the females have acquired their sexual maturity and make the egg-laying flight towards fields and meadows in the opposite direction to that of the pre-feeding flight. Each female deposites about 20 eggs in the soft soil , at a depth of between 1- to 15 cm. Many egg-laying females die, but about a third return to feed and lay for a second time: some lay for a third time. Embriyonic development lasts 4-6 weeks. Larva directly after its hatching, end of June-July, the young larva starts to gnaw the rootlets. It moves about horizontally distances of up to 30 cm per day. When the first cold weather appears, it buries itself in the ground and hibernates. The second year, it surfaces from mid-April and resumes its feeding; it is then extremly voracious. In October, the second period of deep hibernation begins. In the third year, the chafer grub resumes feeding near the surface until July; it then buries itself deeper in the ground and pupates.The adults are formed in August but remain inactive until the next spring. They pupate in a small cell at a depth of 30-40 cm.
The adults are only occasionally harmful on leaves. The larvae destroy the underground parts of the plants and the damage is greatest during the year which follows the laying. The presence of larvae is revealed in meadows by reddenings of large zones where the grass pulls away in tufts. The roots of fruit or forest trees are peeled.
DE: Maikafer, Feldmaikafer, ES: Abejorro comun, FR: Hanneton commun, IT: Maggiolino, GB: Common cockchafer, TR: Mayýs böceði