European Chafer

The European chafer has a 1-year life cycle. The imago, or adult beetle, stage is quite short, lasting 1–2 weeks. The adults come out of the ground in late spring and mate in large swarms, usually on low trees and shrubs. The beetles are most active on warm, clear nights when the temperature is above 19 °C (66 °F). They emerge at about 8:30 pm, mate through the night, and return to the soil by daybreak. Beetles may return to the trees to re-mate several times over the mating period. Late in the period, the adult carcasses may litter the ground beneath trees used for swarming. Female chafers lay 20-40 eggs over their lifespan. They are laid singly, 5–10 centimetres (2–4 in) deep in moist soil, and take 2 weeks to hatch. The grubs hatch by late July. The grub population consists mainly of first instars in early- to mid-August, second instars by early September, and third instars by mid-September to early October. In frost zones, the grubs feed until November, then move deeper into the soil. In frost-free areas, the larva will feed all winter. Vigorous feeding occurs from March through May. In early June, the grubs again move deeper, from 5–25 centimetres (2–10 in), to form earthen cells and pupate. The pre-pupal and pupal stages last 2–4 days and 2 weeks, respectively. By June, the new beetles begin emerging.