Cicadas are back with a vengeance

Spring into spring with billions of cicadas! This year, the U.S. will see the emergence of two large broods of cicadas, which have not emerged simultaneously in more than two centuries. The ecological phenomenon could give rise to new species of cicadas and provide nutrition for several local animals. And while the insects are harmless to humans and animals, they will absolutely be seen and heard in the coming months. 

Insect invasion

Billions of cicadas are expected to make an appearance in the East Coast and Midwestern U.S. this April as two broods of the insect emerge. Cicadas are periodical insects meaning they "spend most of their life underground in an immature nymph form before surfacing from the ground every 13 or 17 years for a brief adult life," NPR said. The two broods making an emergence this year are Brood XIX, or the Great Southern Brood, which emerges every 13 years, and Brood XIII or the Northern Illinois Brood, which emerges every 17 years. The prior is also the largest periodical cicada brood. "It's rare that we see this size of double-brood emergence," Jonathan Larson, an entomologist and assistant professor at the University of Kentucky, said to CNN. "We're talking about an absolute oddity of nature, one of America's coolest insects."

While double-brood emergence happens often, it has been more than 200 years since these two broods have emerged together, and it will not happen again for another 221 years. Periodical cicadas differ from annual cicadas, a brood that tends to appear every summer around August. Periodicals appear earlier in the year and not nearly as often. "It's like a graduating class that has a reunion every 17 or 13 years," Gene Kritsky, professor emeritus of biology at Mount St. Joseph University and author of "A Tale of Two Broods: The 2024 Emergence of Periodical Cicada Broods XIII and XIX," said to NPR. 

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A constant buzz

While the emergence will be the "most macabre Mardi Gras that you've ever seen," according to Larson, the cicadas themselves are essentially harmless. The insects "don't sting or bite and are not poisonous," and can be a "great food source for birds and are nutritious for the soil once they decompose," Time said. They can be annoying though. "You should expect lots and lots of cicada exoskeletons to be covering your trees and shrubs," Larson said. "You should also expect to hear lots and lots of noise."

The cicadas emerge in order to breed and then die promptly after. The broods also consist of multiple species of cicadas. "The outcome of this will produce hybrids, and only the cicadas and Mother Nature know what the outcome will be," Mike Raupp, a professor emeritus at the University of Maryland's entomology department, said to BBC. Female cicadas lay eggs in trees, which could be harmful to young trees, but damage can be mitigated by using cicada nets. Despite this, "their emergence tunnels in the ground act as a natural aeration of the soil" and "provide a food bonanza to all sorts of predators, which can have a positive impact on those populations," according to Cicada Safari.

Geographically, the broods of cicadas may only see minor overlap. Brood XIII will emerge in northern Illinois, southern Wisconsin, eastern Iowa and northwest Indiana. Brood XIX will emerge in parts of Illinois, Missouri, Kentucky, Tennessee, Virginia, Maryland, North Carolina, South Carolina, Georgia, Alabama, Mississippi, Louisiana and Arkansas. Areas in central Illinois are most likely to see both broods emerge around the same time. "If you're lucky enough to live in an area where these things are going on, get your kids out there," Kritsky said to NPR.