When will cicadas emerge in Illinois? Billions of insects arrive this spring

CHICAGO (CBS) -- The Chicago area is set to see billions of cicadas if not more this spring.

With Illinois the center of emergency, the area will see more cicadas than anywhere else in the country. Experts said there will be no avoiding the insects, but there are ways to prepare for them.

Right in the middle of May, the first sign of the arrival will be cicada shells – shed once the cicadas emerge. They will be everywhere, and will be seen before the cicadas are heard.

How many cicadas will be in Illinois? 

And heard they will be. Cicadas are quite noisy.

"It's going to be this mass invasion, but a peaceful one," said Allen Lawrence, associate curator of entomology at the Peggy Notebaert Nature Museum.

The museum has an assortment of cicada specimens on display – including some enormous ones from Malaysia. The cicadas coming to the Chicago area this spring will not be nearly as big.

Nonetheless, Lawrence said, they will be "everywhere."

He said billions - possibly trillions - of cicadas will buzz around the city and the entire state. Two different broods of cicadas will crawl out of the ground at once, Lawrence said, "and come out all together in this mass emergence."

Experts say this has not happened since 1803.

"It's historic, especially for Illinois, because two broods are emerging right next to each other," Katie Dana, an affiliate with the Illinois Natural History Survey at the University of Illinois, told CBS 2.

Although the number is in the billions, in most places, the cicadas will be spread out. "Anywhere that there were trees 17 years ago, there's going to be a lot of cicadas, presumably. If people remember from 2007, that's a good indicator of where they will be again," Dana said. 

Whether people find their mating call buzz akin to singing or screeching, there will be no escaping it for about a month. Everyone will also be seeing and dodging cicadas for that month.

In the Chicago area, Brood XIII is coming after 17 years underground. They were last seen in 2007, and before that in 1990.

In Springfield, Brood XIII will be joined by Brood XIX, which comes out after 13 years underground.

Will cicadas get into your home? 

Plant roots sustain cicadas. Thus, Lawrence said they will not be emerging from any part of anyone's home.

"They will definitely be in people's yards. They will be all around people's homes," Lawrence said. "But they're not likely to get into your home."

"They're pretty big, so it's not like they're gonna be coming in through tiny holes," Dana seconded. 

Are cicadas dangerous? 

Cicadas aren't toxic, They don't bite or string, and they won't go after your garden. But anyone who has recently planted a tree is advised to put a cover over it now.

Cicadas are actually good for the soil and thus for lawns. They are also good for wildlife, according to the Environmental Protection Agency, which is already warning pesticides aren't effective against the cicadas.

"These insects are so important to so many other animals," Dana said, especially insectivorous birds that are on the decline.

"Leave them alone," Lawrence said. "They will go away eventually."

How long will cicadas last? 

And when they do, Lawrence said it is a good idea to keep a snow shovel handy.

"You will find piles of their bodies scattered around," Lawrence said. "You may have to shovel them off your sidewalk."

Another place to check for cicada pileups is in gutters. Dana suggests throwing them away into the compost bin.

The cicadas are expected to clear out by the end of June. Later, as happens every year, annual dog-day cicadas will arrive to provide a twilight lullaby to the Chicago area from July through September and into October.