Life Cycle

Most June beetles have 2- or 3-year life cycles, although a few species have cycles lasting 1 or 4 years. Adults typically are active from April to June. The beetles emerge after sundown and fly to the tops of trees to feed and mate, returning to the soil before dawn. They are clumsy fliers and often are attracted to outdoor lights. Mated females fly to turf, pasture, or agricultural fields and burrow down 5 to 15 cm to lay eggs in the soil. Each female lays 20 to 50 eggs in her lifetime. Eggs are pearly white, about 2.5 mm long, and elliptical at first, becoming more spherical as the embryo develops. Hatching occurs in about 3 weeks, and the young grubs begin feeding on fine roots and organic matter.

Larvae of species with 2-year cycles typically overwinter as second instars. They resume feeding in early spring, molting again in April or May. Third instars attain their full size by summer's end. Pupation occurs underground, in an earthen cell. Most species transform to adults by late autumn, but the beetles remain underground until the following spring. Grubs of species with 3-year cycles feed throughout the first two summers, hibernating twice and pupating midway through the third summer. Their adults are usually fully formed by autumn but do not emerge from the soil until the following spring. Because of overlapping generations and presence of more than one species, several sizes of June beetle grubs may be found together at a given site.

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