The late summer cicada buzz is starting a little earlier this year. The periodical cicada broods XIII and XIX (the Northern Illinois and Great Southern Broods, respectively) will emerge simultaneously from late April through June across much of the Midwest and South for the first time since 1803.
“It’s so infrequent that we’re able to observe something like this in nature,” said Zach Schumm, insect diagnostician at Iowa State University’s Plant and Insect Diagnostic Clinic. “The eastern half of the United States is the only location that has these periodical cicadas. So it’s a very unique sort of… ecological phenomenon.”
This co-emergence happens every 221 years, when Brood XIII’s 17-year cycle and Brood XIX’s 13-year cycle align. Brood XIX is the largest of all periodical cicada broods, and the last time Brood XIII emerged, Chicagoans had to get out their shovels to clear the carcasses.
What is a periodical cicada?
Periodical cicadas — named for their periodical life cycles — live most of their lives underground. They start life as eggs laid in tree branches. Once they hatch, the cicada nymphs burrow into the ground near tree roots and feed on the sap. They stay there for 13 or 17 years, depending on which brood they’re a part of, finally emerging for six to eight weeks to mate. Then they die while their eggs hatch to start the cycle over again.
Many scientists believe that the 13- and 17-year life cycles and synchronous emergences are an evolutionary adaptation to escape predation, but there has been no decisive conclusion on the matter.
“You know, organisms can generally do a lot better if they emerge en masse, because when there’s 10 million of you or more sitting outside, there’s too many of you for predators to consume all of you,” Schumm said.
Periodical cicadas are different from annual cicadas, which can be found on almost every continent — not just in the eastern U.S. They’re in the same family as periodical cicadas, but are a different species with some unique characteristics. Annual cicadas have a one-year life cycle, usually emerging in July and August. They also buzz at dusk, rather than in the morning.
Where can I find Brood XIII and XIX?
Eastern Iowa and Illinois will see both broods, though they’re unlikely to cross over anywhere except the Springfield, Illinois area. Brood XIX will also appear throughout Missouri, while Brood XIII may appear in small pockets of southern Wisconsin. Regardless of where you live, you’re unlikely to see either of these cicada broods in your backyard like some states did in the 2021 Brood X emergence.
“Not everyone’s just going to experience them like emerging en masse … [or] covering their house,” said Schumm. “That’s unlikely to happen unless you’re really close to a wooded lot.”
Donald Lewis, professor emeritus of entomology at ISU, explained that periodical cicadas tend to live in older wooded areas and that broods are getting smaller each year as human development clears woodland.
“Periodical cicadas emerge only in longstanding, undisturbed wooded areas — woodlands, river valleys, etc.” Lewis said. “If the trees in an area were removed during the past 200 years, the cicadas were too. Periodical cicadas will not emerge in farm fields [or] urban developments.”
If you’re interested in cicada hunting, Schumm suggests looking at one of the publicly accessible cicada maps and zooming in to see where they're most concentrated. In these areas there may be tens of thousands of cicadas per tree and millions per acre.
“If you’re in any place that is … any sort of wooded area, that’s going to increase your chances of finding them,” Schumm said. “What I always tell people is if you’re driving slow enough and your window’s open, you’ll be able to hear them for sure. Just always go towards the sound because they’re very, very noisy.”
Should I be worried about cicadas in my garden?
The short answer is: No. Cicadas don’t bite or sting and, aside from the minimal damage their egg-laying does to tree branches in wooded areas, they don’t pose a threat to the landscape. In fact, because they burrow out of the ground, they naturally aerate the soil.
“As an entomologist, I spend a lot of time trying to appreciate insects and what they do and how they are,” Schumm said. “A lot of people don't think like that, but I try to encourage it. It’s okay to get close to them and look at them and pick them up and touch them.”
Schumm encourages Midwesterners to experience the cicadas, even if the thought of millions of bugs seems unappealing.
“I feel like I always hear stories when periodical cicadas come out — people are kind of in panic mode,” Schumm said. “But you're experiencing something that exists nowhere else in the world. It's not going to happen for another 200 years.”
