If you've lived in the Eastern U.S. since 2004, you may experience déjà vu in a few months. The billions of periodical cicadas that make up Brood X will emerge from the earth for the first time in 17 years in the summer of 2021, Newsweek reports.
Periodical cicadas go through lifecycles of either 13 or 17 years. The appropriately named 17-year cicadas live for 17 years as nymphs, feeding on sap from roots underground. When the weather warms up in their 17th year, they emerge to finally molt into their mature form, reproduce, and die after a brief adult life.
Different cicada broods operate on different 17-year cycles. Brood X, or the Great Eastern Brood, is the most widespread cicada brood in the U.S., with a range spanning Delaware, Georgia, Illinois, Indiana, Kentucky, Maryland, Michigan, North Carolina, New Jersey, New York, Ohio, Pennsylvania, Tennessee, Virginia, West Virginia, and Washington, D.C. When the soil hits 64° F this spring, the Brood X cicadas will crawl up to the surface by the billions.
The precise time the cicadas emerge depends on the weather, but locals living in their range will know it when they do. The first thing cicada nymphs do when they're out of the ground is scale the closest vertical surface, whether it's a tree, a screen door, or someone's leg. After molting into their adult form, they make their presence known with their deafening mating calls. These choruses can exceed 100 decibels, which is equal to a car stereo blasting at max volume.
Whether you love them or can't stand them, this batch of cicadas won't stick around for very long. Their reproduction cycle lasts just a few weeks, after which their bodies will drop back to the earth from which they came.