There are about 86 species of scarab beetles found in eastern North America. Adult beetles are quite large 1/2-1 1/4 inch, emerging from the soil at the end of spring, usually in June, hence the name. The adult female buries 60-75 eggs in the soil over a 2 week period, hatching as larvae, feeding on plant roots and decayed matter. These larvae are the white grubs often seen just under the turf and are a favorite food for skunks, voles and birds such as crows. After 1-3 years as larvae, pupation occurs and the adult emerges and the cycle begins all over.
While not harmful to humans per se, adults are voracious leaf eaters and can cause damage to gardens, pastures and golf courses. The grubs, being root eaters can destroy lawns in conjunction with certain mammals which will dig up the turf looking for them.