The World Hasn’t Seen Cicadas Like This Since 1803

The cicadas are coming — and if you’re in the Midwest or the Southeast, they will be more plentiful than ever. Or at least since the Louisiana Purchase.

This spring, for the first time since 1803, two cicada groups known as Brood XIX, or the Great Southern Brood, and Brood XIII, or the Northern Illinois Brood, are set to appear at the same time, in what is known as a dual emergence.

The last time the Northern Illinois Brood’s 17-year cycle aligned with the Great Southern Brood’s 13-year period, Thomas Jefferson was president. After this spring, it’ll be another 221 years before the broods, which are geographically adjacent, appear together again.

“Nobody alive today will see it happen again,” said Floyd W. Shockley, an entomologist and collections manager at the Smithsonian National Museum of Natural History. “That’s really rather humbling.”

These insects will begin to appear in late April. They’ll use their forelegs to tunnel out from the earth, their beady red eyes looking for a spot where they can peacefully finish maturing. A few days after they emerge and molt, the males will start buzzing in an effort to find a mate, a slow-building crescendo of noise that in a chorus can be louder than a plane.