Cicadas' chorus of buzzing has begun in Chicago

Love 'em or hate 'em, you won't be able to ignore the cicadas' chorus this summer.

After 17 years underground, the periodical cicadas have emerged in northern Illinois and their telltale chorus of buzzing has begun in some parts of the Chicago area.

At the Morton Arboretum in Lisle, the cicadas haven't emerged at their peak levels yet and aren't as widespread as they will be later in the season, but some buzzing has begun, according to Stephanie Adams, plant health care leader. Depending on the exact location, the peak emergence is expected sometime in the next few weeks.

When will I hear the noise?

While the cicadas that have emerged in recent weeks differ from the annual cicadas that come each summer, Adams said, they carry a similar tune.

"The sound outside reminds me of the end of summer ... when you hear the nice buzzing," she said. "There's a couple different sounds: there's different chirping and buzzing, [and] there's fluctuations of pitch and intonation in them. It does fluctuate throughout the course of the day."

Often a marker of dusk on long summer days, the buzzing of the annual cicadas, or "dogday" cicadas, typically stretches through the late afternoon and evening, but periodical cicadas will buzz during the day when the weather is warmest, said Tom Tiddens, supervisor of plant health care at the Chicago Botanic Garden in Glencoe. The annual cicadas are also not quite as loud as the periodical cicadas are expected to be.

The Chicago area began seeing its first periodical cicadas early last week, and the peak emergence hasn't happened yet, and isn't expected for at least another week depending on the exact location. The noise will continue to grow as more cicadas come up from underground, then will taper off near the end of their cycle aboveground, Tiddens said.

"We're just starting to hear some of that, as the days go on it's going to get a little bit louder," Tiddens said. "Warmer sunny days will drive them to be more active, more noisy. Cloudy day will be a little bit less [noisy]."

Where will I hear the cicada chorus?

Cicadas congregate around trees that are ideal hosts to lay their eggs, so they're mostly found in wooded areas. Forest preserves, parks and other wooded spots will likely be where cicadas will be the loudest in the area this season.

It's rare to find the insects within Chicago city limits because so many trees have been cut down in the last century and cicadas don't travel more than a half-mile from where they emerge, Jim Louderman, collections assistant at the Field Museum's Gantz Family Collection Center, told the Chicago Sun-Times.

"Because almost all of Chicago proper has been cut in the last 100 years, there's really only a few pockets in the city where they'll sing," he said.

Edison Park, Montrose Point Bird Sanctuary and some older city parks with older trees could see some of the emergence, he said.

Why do cicadas buzz?

Male cicadas, which "sing" to attract females during the mating process, have a drum-like organ underneath their wings, called a thimble, Louderman said. Females don't make any noise outside of a slight clicking.

Within the 17-year brood of cicadas, there are three species in northern Illinois. Each species rubs the segments of the organ together at a different rate to produce a different tone in order to attract mates of their own species, Louderman said.

Male cicadas of a particular species will gather around a specific tree, then sing together to create a "chorus," Adams said. The females will then follow them to that tree, and choose their mates.

"It's a mating call, just like birds," Adams said.

How loud will it be? What does it sound like?

The noise level will depend on location, temperature and how many cicadas are around, experts said.

When it's warm and sunny and the noise is at its loudest, the buzzing can surpass 100 decibels. At the lower end, the cicadas will be around 85 decibels, Louderman said.

The noise level is comparable to a lawnmower or chainsaw, and it could cause hearing damage, Adams said. She recommends wearing ear plugs if you need to be outside near a mass of cicadas.

"The tone of a lawnmower is similar to a tone of a cicada," Tiddens said. "I've had people tell me they're out with their lawnmower and they're attracting cicadas."