Every 17 years, Brood X cicada nymphs tunnel upwards en masse to emerge from the surface of the ground. The insects then shed their skins on trees and other surfaces, thus becoming adults. The mature cicadas fly, mate, lay eggs in twigs, and then die within several weeks. The combination of the insects' long underground life, their nearly simultaneous emergence from the ground in vast numbers and their short period of adulthood allows the brood to survive even massive predation.