The cockchafer, a common European beetle, often captures attention with its distinct appearance and buzzing flight during spring and early summer evenings. These insects have been a recognizable part of the European landscape for centuries, sometimes even featuring in folklore due to their periodic large emergences.
Identifying the Cockchafer
The adult cockchafer, scientifically known as Melolontha melolontha, is a large beetle, measuring between 25 and 30 millimeters in length. It possesses a robust body with a black head and a black thorax, covered in short hairs. Its most recognizable features include reddish-brown wing cases, called elytra, that meet in the middle and have four longitudinal ribs, along with characteristic fan-like antennae. These antennae are more pronounced in males, serving a sensory role in detecting pheromones released by females. Other common names for this beetle include May bug or May beetle, reflecting its emergence period, and sometimes doodlebug.
Life Cycle and Habits
The cockchafer undergoes a complete metamorphosis, progressing through egg, larval, pupal, and adult stages. Female beetles lay their eggs in the soil, burying them 10 to 20 centimeters deep, with each female laying between 60 and 80 eggs. After four to six weeks, the eggs hatch into larvae, known as white grubs, which are creamy-white, C-shaped, and possess a brown head with strong mandibles. These grubs reside underground for an extended period, usually three to four years, up to five years in colder climates, feeding on plant roots.
As they grow, the grubs can reach lengths of 40 to 46 millimeters before they pupate in early autumn, transforming into adult beetles within six weeks while still underground. The newly formed adults remain in the soil over winter, emerging the following spring, from late April to July. Adult cockchafers are active for five to seven weeks, during which they feed on the leaves and flowers of deciduous trees, such as oak, maple, and beech. Their flight is noisy, especially at dusk, as they seek mates and feeding grounds.
Ecological Influence
Cockchafer populations play a role in their ecosystem, but their activities can also significantly impact human interests, particularly in agriculture. While adult cockchafers feed on tree leaves, causing defoliation, the most substantial damage occurs during their prolonged larval stage. The white grubs consume the roots of various plants, including agricultural crops like cereals and grasses, as well as garden plants and lawns. This root feeding can lead to stunted plant growth, wilting, and in severe cases, the death of plants, causing considerable economic losses for farmers.
Natural predators help regulate cockchafer populations; birds such as rooks and other corvids, moles, and certain parasitic flies and fungi prey on the grubs. The presence of damaged lawns, characterized by yellow patches or areas dug up by animals, often indicates a grub infestation. While management strategies exist to mitigate their impact, the long underground larval stage presents a challenge for control.