Cicada exoskeletons cling to a tree in Bibb County, Ga., April 25, 2011. (Jason Vorhees/AP)

After 13 years spent under the ground, huge populations of cicadas in the southern U.S. will rise to the surface during the next few weeks. They’ve already shown up in Georgia.

After crawling up tree trunks in nymph form, they’ll wriggle out of their shells, start to fly, sing their anything-but-pleasing mating tune, and breed millions more cicadas.

By July, the adults will all be dead and their children will be underground to wait out the next 13 years.

Broods of cyclical cicadas appear ever 13 to 17 years, occupying certain geographic areas. This southern U.S. batch of cicadas is from periodical cicada Brood 19.

Although the appearance of cicadas can be creepy, with their orange eyeballs, veined wings, and ghostly shells, they’re don’t bite or sting and they’re harmless to humans. Cicadas are even somewhat healthy to eat, which some people do.

See below if you don’t believe us: