European chafer

European chafer adults are 1/2 inch long. Males and females are a uniform tan or light brown color. Larvae are typical C-shaped white grubs, reaching a maximum size of 1/4 inch wide and 1 inch long.
Most European chafer grubs complete development in one year, but a small proportion of the population may require two years to complete development. Adult beetles emerge from the soil between the middle of June and early July in Michigan and New York. Emergence may be two to three weeks earlier in southern Ohio, Pennsylvania and New Jersey. They fly on warm evenings (above 65 degrees F) for several hours just before and after sunset. Adult activity peaks within two to three weeks of first emergence. Eggs are deposited 2 to 4 inches below the soil surface. First instar (or larval stage) grubs emerge from eggs in early August and molt to second larval instar by the middle of August. By September 1, nearly all grubs are second instar (1/2 inch long), and by October 1, most of the larvae are mature, third instar grubs (3/4 to 1 inch long). They continue feeding on turf roots until the soil surface freezes (usually sometime in November).
Overwintering grubs remain just below frozen soil. On average, 24 percent of the grubs do not survive the winter. Surviving grubs return to the surface as soon as the ground thaws, feeding on grass roots again in late winter and spring. By late May, almost all of the grubs move down to a depth of 2 to 10 inches to pupate. They remain as pupae for about two weeks before emerging as adults. Wet soil during pupation may cause high mortality.
Natural control of European chafer by predators, parasites and pathogens is excellent in Europe but poor in the United States. Several parasites, including four species of flies and two wasp species, have been released with little success. Natural enemies reported in the United States include two species of ground beetles that feed on grubs and eggs, a protozoan pathogen and a rickettsia pathogen.