Egg -- When the egg is first laid, it is pearly white and elliptical, measuring 1.5 mm wide and 2.1 mm long. It gradually becomes more spherical as the larva inside develops.
Larva -- The newly hatched larva is 8 mm long and grows to a length of about 40 mm. Whitish with a brownish-black head, it has conspicuous brown spiracles along the sides of its body.
Pupa -- The brown pupa, approximately the same shape as the adult, becomes metallic green just before the adult emerges. It is about 15 mm long and 15 mm wide.
Host Plants. -- Green June beetle adults prefer ripening fruits of many plants. The larvae feed on decaying organic matter in the thatch and root zone of many grasses, as well as on the underground portions of other plants such as sweet potatoes and carrots.
Damage -- Adult and larval feeding on economic crops causes some financial loss; however, the larvae's tunneling for feed and the adults' burrowing into the soil each night cause more serious destruction. The tunneling uproots young plants. The many exit holes of the adults and larvae resemble ant hills and mar lawns and golf course greens.
Life History -- Unlike the May beetles, only one year is required for these beetles to complete their life cycle. They overwinter as larvae that may become active on warm winter days. They increase their activity in the spring, and in June pupate in earthen cells several centimeters underground. The pupal stage lasts about 18 days; adults appear in July and August. In mid-summer, adults lay eggs underground in earthen balls. Each female lays 60 to 75 eggs over a span of about two weeks. About 18 days after the eggs are laid, they hatch into small, white grubs. The larvae molt twice before winter. The third larval stage lasts nearly 9 months, after which pupation occurs. At night, the larvae may be found on the ground crawling on their backs. This curious form of locomotion is peculiar to the green June beetle.