In the eastern half of the United States, periodical cicadas come up out of the ground every 17 years when the ground warms up to 64°F. They are expected to be seen here in the Washington, DC area in May of 2013. They are large insects, about an inch and a half long, with black bodies, red eyes and delicate wings. There are far too many to count. You see them everywhere--on the sidewalk, on the trees, on the porch, on the street.
Cicadas of the same life cycle are known collectively as a single "brood". There are 12 broods of 17-year cicadas. As a result, it is possible to find cicadas in almost any year by traveling to the appropriate location. The group expected in the capital region this spring, known as Brood 2, are the offspring of cicadas last seen in 1996.
Usually in early to mid-May, the cicada nymphs crawl out of the ground, onto trees and shed their skins. The males sing very loudly to attract female mates. The females lay their eggs in the branches of trees. The nymphs hatch and burrow several inches underground. The above ground cycle lasts less than four weeks. Beginning in mid-June, the adults all die. Male cicadas die soon after mating. Females lay 400 to 600 eggs before they die.
Fortunately, Cidadas don't bite or sting so they're not harmful to people or pets. They generally leave no lasting damage, except possibly to young trees and shrubs. They are annoying to most, though some people find them and their unique life cycle to be fascinating.
Read More About the Broods of the Periodic Cicada