WTTW News Explains: Why Will There Be So Many Cicadas in Illinois This Year?

Who’s “flyover country” now?

In April, a total solar eclipse captivated the country, with southern Illinois smack in the path of totality. Now, another natural phenomenon is happening in the state.

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The spectacular solar show is being followed by a highly anticipated, truly once-in-a-lifetime invasion of insects that, depending on one’s personal stance on bugs, will either spark delight or horror.

In case you haven’t heard, the cicadas are coming, and things are about to get loud.

Now maybe you’re wondering, “What’s the big deal? We get cicadas every year.”

It’s true that annual cicadas, also known as dog day cicadas, turn up every July or August, just to remind us that summer’s almost over.

But there’s another kind of cicada, called periodical cicadas. And that’s the story in 2024.

Periodical cicadas are more like reclusive rock stars. They disappear underground for years, living off of tree roots and then emerge topside to loads of media hype. They even have the bloodshot eyes to complete the look.

These periodical cicadas are grouped into 15 different broods, scattered across the eastern U.S.

Each brood has a different alarm clock of sorts, set on either a 13-year or 17-year cycle. When the alarm goes off, the entire brood busts out of hiding so they can hurry up and mate and die.

Here’s where things get crazy: This spring, two different broods in Illinois are getting their wakeup call at the same time. 

A 13-year brood in southern Illinois and a 17-year brood in northern Illinois will make their first joint appearance in more than 200 years. The last time this happened, Illinois wasn’t even a state!

Before you picture skies darkened with trillions of insects, don’t worry — the broods don’t really overlap geographically, so two broods doesn’t equate to double the cicadas. 

In places where the ground has been disturbed a lot over the years, like Chicago, people will miss out on most of the fun.

And by fun, we mean lawns and trees blanketed with cicadas, screaming at the tops of their lungs. 

Actually, all that noise comes from male cicadas doing a serious core workout. They have a special body part that they vibrate by contracting tiny muscles hundreds of times per second, then they use their abdomen like an amp, cranking up the sound to lawnmower-levels on the decibel chart.

Believe it or not, this ear-splitting racket is the fellas’ mating song, and lady cicadas dig it.

One thing leads to another, and the next thing you know, a new generation of baby cicadas hatches, burrows underground and the whole cycle starts all over again.

See ya in 2041!

Note: This article was originally published April 17, 2024. 

Contact Patty Wetli: @pattywetli | (773) 509-5623 |  [email protected]

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