Rare cicada co-emergence could be big bug blowout for Chicago

The big picture: Trillions of cicadas will probably emerge nationwide this year, though population sizes are extremely difficult to predict, writes Axios' Jacob Knutson. The cicadas will swarm 16 states, including Illinois.

• Cicadas have long burrowed in northern Illinois because of the prairie. Because they fly only a half a mile or so once emerged, they've stayed in our area for centuries.

What they're saying: "Expect a lot of noise, and expect to see a lot of action," Allen Lawrence, an associate curator of entomology at Peggy Notebaert Nature Museum, tells Axios.

• "This emergence will be patchy. In one neighborhood, you may have a massive amount of screaming cicadas all over trees and the sidewalks, and in another it may be quiet."

Yes, but: Despite the historic co-emergence, there probably won't be an abnormal amount of cicadas this year, according to the University of Connecticut.

• Brood XIII and Brood XIX are both set to pop up when the ground gets warm, usually around May or June. They'll emerge at the same time, but their ranges don't significantly overlap, meaning cicada density should appear normal.

Zoom out: The cause of mass cicada emergencies is still being researched, but it is believed to have evolved in response to predators.

• Because they're eaten by pretty much everything — even some fungi — and have few ways to defend themselves, cicadas may have adapted to erupt from the ground in such large amounts that predators couldn't consume them all.

The bottom line: They're coming this spring, but at least they aren't killer bees.