The 13-year and 17-year broods that will emerge from underground this spring will be appearing together for the first time in 221 years.

This spring, Brood XIII and Brood XIX of periodical cicadas will emerge together for the first time since 1803. JanetandPhil via Flickr under CC BY-NC-ND 2.0 DEED
Billions of cicadas from two different broods will emerge this spring in a rare, buzzy natural phenomenon that hasn’t happened since 1803.

The insects belong to two distinct populations of periodical cicadas: one that surfaces from underground every 13 years and another that emerges every 17 years. The last time these specific groups—called Brood XIII and Brood XIX, respectively—lined up their cycles and appeared at the same time, Thomas Jefferson was president, reports NBC News’ Denise Chow.

Though some cicadas surface every year, periodical cicadas spend most of their lives underground before emerging en masse every 13 or 17 years to mate and start the cycle over again.

Any pair of broods may occasionally overlap and emerge in the same year. But these specific groups—Brood XIII (also known as the Northern Illinois Brood) and Brood XIX (or the Great Southern Brood)—only appear simultaneously once every 221 years, making 2024 an especially exciting period for entomologists and bug aficionados alike.

The next time the broods align again will be in 2245.

“Nobody alive today will see it happen again,” says Floyd W. Shockley, an entomologist and collections manager at the Smithsonian’s National Museum of Natural History, to the New York Times’ Aimee Ortiz. “That’s really rather humbling.”
Brood XIII (blue dots) and Brood XIX (red dots) will likely overlap in central Illinois and eastern Iowa. Gene Kritsky / Mount St. Joseph University

The two broods will also overlap geographically: Though at least some of the cicadas will emerge across the Midwest and Southeast, members of both groups are expected to converge in parts of central Illinois and eastern Iowa.

All told, scientists estimate more than one trillion cicadas will be buzzing around a 16-state area, with the greatest numbers emerging in forested regions and urban green spaces. Lined up end-to-end, one trillion cicadas would span 15,782,828 miles—long enough to cover the distance to the moon and back 33 times, per the New York Times.

Cicadas typically appear above ground once soil temperatures reach 64 degrees Fahrenheit. In some places, that could occur as early as late April, and the insect spectacle will likely continue on a rolling basis through May and June.

Once they crawl onto the surface, the nymphs will ditch their exoskeletons—leaving crunchy cicada-shaped shells in their wake—and start flapping their wings. They’ll spend the next six weeks or so making their cacophonous mating calls so they can lay their eggs before they die. In the meantime, they’ll also provide a smorgasbord for birds—and give caterpillars a brief respite from predation in the process. Later, when the cicada eggs hatch, nymphs will emerge and tunnel underground to start the broods’ cycles anew.

The rare, synchronized event should be finished by early July, meaning residents of affected states will once again be able to enjoy some peace and quiet. Cicadas’ mating songs can reach nearly 100 decibels, which is similar to the sound intensity of a chainsaw or a motorcycle.

“It’s pretty much this big spectacular macabre Mardi Gras,” says Jonathan Larson, an entomologist at the University of Kentucky, to NPR’s Clare Marie Schneider. “It’s a lot of singing, lots of paramours pairing up and then lots of dying.”
Cicadas are beneficial to their habitats. Gene Kritsky / Mount St. Joseph University
The broods are expected to draw some bug-curious travelers to the overlapping emergence areas in the Midwest. But some residents of those regions may be less than enthusiastic about the multi-week onslaught of bugs.

“I’ve talked to half a dozen people already who want to go on vacation and come into the area to seek the cicadas,” says Gene Kritsky, a biologist at Mount St. Joseph University and the author of A Tale of Two Broods: The 2024 Emergence of Periodical Cicada Broods XIII and XIX, to NBC News. “In years past, I’ve also helped people plan vacations to leave while the cicadas are here.”

Some of those tourists will be scientists hoping to study everything from the bugs’ range to their reproductive behaviors. For instance, entomologists are curious to know whether the two groups will interbreed, which could possibly lead to the creation of an entirely new brood.

As for people living in the emergence zones, scientists recommend simply leaving the cicadas alone—and, if possible, cherishing this once-in-a-lifetime spectacle. Cicadas don’t carry diseases, bite or sting, and their presence benefits the broader ecosystem. For example, when they tunnel up from underground, they help aerate the soil. When they shed their exoskeletons and, later, die, their bodies provide nutrients to plants. They also naturally prune trees when laying eggs in their branches.

The dual emergence will be like “having a David Attenborough special in your backyard,” Kritsky tells NPR.

“If you’re lucky enough to live in an area where these things are going on, get your kids out there,” he adds. “Watch this.”