The east coast is preparing for one of nature’s greatest spectacles. A gigantic swarm of periodical cicadas is due to emerge from underground for the first time in 17 years. Known as Brood X (or the Great Eastern Brood), this particular swarm is estimated to include billions of cicadas that have been developing underground since 2004.
According to Scientific American, only 15 periodical cicada broods exist worldwide, all of which occur in the eastern United States. Some periodical broods have 13-year cycles, and according to NBC News, two broods are extinct, and one is currently declining (XI and XXI are extinct; VII is declining). In addition to periodical cicadas, the east coast is home to annual cicada species that can also be seen and heard along the east coast during late spring and early summer months.
Timing estimates vary with reports, but sources think that Brood X will emerge in late April to early June and bring a cacophony of mating sounds throughout 15 states. The emergence occurs when the soil warms to a temperature suitable for cicada nymphs. According to Reuters, the nymphs survived off nutrients from tree roots for 17 years. Once they crawl out of the ground, they shed their skin and begin their mating cycle.
According to Scientific American, the singular goal of this swarm is to generate the next brood. Reuters reports that males make the infamous loud, chirping sound by vibrating a plate on their abdomen. They want to chirp as loud as they can for as long as possible to attract female mates. Once they mate and lay eggs, the periodical cicadas die. Scientific American reports that once the new eggs hatch, they’ll fall from the trees and burrow in the soil to begin feeding on roots and restart the exceptional life cycle.
Scientists agree that there isn’t a solid explanation for this long life cycle, but they suspect it is due to predator avoidance. Scientific American states that some scientists think that the life cycle evolved in response to glacial cycles tens of thousands of years ago. As for how cicadas know when to emerge, Scientific American reports that some scientists believe that cicadas get signals from root systems.
Although noisy and numerous, these natural wonders are harmless, and reports encourage residents within swarm areas not to kill the cicadas. They’ll only be around for four to six weeks, and then not again for 13 or 17 years!