Billions of Cicadas Set to Emerge in Illinois This Summer

The sound of summer in Chicago this year won’t come from the radio but instead will ring out from the trees as Illinois is set to be the epicenter of a rare ecological event when two groups of periodic cicadas will emerge from the ground at the same time. 

The typical buzzing sound of cicadas associated with summer will be more intense this year, as for the first time in 221 years insects from two broods, or breeding groups, will unearth together, according to the University of Illinois College of Agricultural, Consumer and Environmental Sciences.

This will be the last time two cicada broods line up in their scheduling in North America until 2245. The first group is Brood XIII, also known as Northern Illinois Brood, which includes species of cicadas which emerge every 17 years. 

Brood XIX, also known as the Great Southern Brood, is the group of 13-year periodic cicadas with the largest geographic footprint, emerging across the Southeast and Midwest from Georgia to Oklahoma and southern Illinois. 

Sarah Ku, an assistant professor in the School of Environmental Sustainability and the Quinlan School of Business whose research interests include insects, said a coincidence with the timing of the periodic cicada broods will cause the double brood event.

“It’s sort of like the eclipse that just happened on Monday,” Ku said. “It’s just the timing that is causing it to happen now. It happens in different parts of the world at different times.”

The millions of cicadas will join in the symphony with the annual cicadas, which emerge every summer in Illinois, and engulf the state. 

“I’ve been in places where they have a lot of cicadas and it is loud,” Ku said. “To me, it’s not an offensive sound or a disruptive sound. It is loud, but it just sounds like summer.”

The cicadas will overlap in a few areas in the central part of the state, while the annual cicadas will emerge later in the summer, according to the University of Illinois. Observers can expect to see cicadas begin to emerge in mid-May and early-June once soil temperatures reach 64 degrees. 

Ku said cicadas emerge in large groups so they can overwhelm the ecosystem and potential predators, ensuring the survival of large numbers of them.

“Cicadas come up in these mass broods because they know that a lot of them will be sacrificed essentially,” Ku said. “So it’s sort of based on numbers that they’re like, ‘Hey, we know not all of us will survive,’ but there is a concerted effort to all be out together so that some mating can happen.”

The cicadas emerge from the ground primarily to breed, according to the University of Illinois. The “singing” passerbyers hear is coming from male cicadas trying to attract a mate. Ku said each species of cicada has their own distinctive sound. 

The “singing” can reach up to 90 or 100 decibels, the sonic equivalent of a lawnmower or L train, and usually begins around five days after the insects emerge, according to the Chicago Sun-Times.

Second-year biology major Arnav Nagpal said he’s expecting a summer of loud noises.

“It’s not going to be fun,” he said. “I’m not a fan of bugs. I hate bees — they scare me to death. Cicadas are pretty big, so I’m not excited at all.” 

George Wiltz, a third-year sports management major, said he’s unsure what to expect with the cicada event.

“It’s kinda crazy to think that trillions of these things are coming from underground,” Wiltz said. “Hopefully it’s not too big of an infestation to the point that it’s bad for the environment.”

After about a month, the cicadas will begin to die, leaving large piles of insect carcasses underneath trees. Ku said the bugs will have a variety of positive effects on the ecosystem, including leaving behind shells and remains as they move through their life cycle, which will provide nutrients for the soil.

“They’re aerating the soil when they come up because they’re tunneling holes when they come up from the soil,” Ku said. “They will also help a lot of populations eat in the sense of birds and squirrels, who are looking for food sources.”

As female periodical cicadas lay their eggs, they cut into tree branches which can pose danger to newly planted trees and shrubs, according to the University of Illinois. As a result, researchers recommend holding off planting new trees until the event has passed or placing netting around small trees and shrubs.

Cicadas are harmless to humans and other animals, and are even edible for humans. Ku, who is interested in consuming insects and studies their viability for sustainable business practices, said she is excited to go out and try new kinds of cicadas. She said she has previously only eaten fried cicadas.

“I’m looking forward to going out and sort of experimenting with some of these things and just seeing how they work in terms of texture and flavor,” she said.

Ku said those interested in eating cicadas shouldn’t look for them in the city, as the pollutants and contaminants in the soil around Chicago poses a risk to humans.

“If people are sort of dead set on trying these or foraging them, going outside of the city into more rural places is a good idea,” she said. “Just so that you have probably less likelihood of getting contaminated soil and stuff that they’re in.”

Ku said there’s also a fungus that infects about 5% of cicadas, so it’s important to make sure to be careful with anything collected in the wild.