Did you know there are 7 species of periodical cicadas in the eastern U.S.? These insects spend nearly their entire lives underground as nymphs, or immature cicadas. When they reach 13 or 17 years old, they emerge from the soil, climb trees and shed their nymph exoskeletons. This year marks the emergence of Brood X, a phenomenon that won't be seen again until 2038. These cicadas emerge in large numbers, reproduce and die, all in a matter of several weeks. Have you spotted any? Video: Pharaoh cic