May 30, 2024

This coverage is made possible through a partnership between WBEZ and Grista non-profit, environmental media organization.

If you live in the Midwest or the Southeast, you know the crickets are coming.

And if you live in Chicago, you know the Cicadalypse is coming.

Cicadas, winged buggie noisemakers whose relatives include leafhoppers and aphids, come in two varieties: the annual cicadas, which are sure to appear every year, and the periodic cicadas, which occur in 13-year and 17-year cycles.

This year, however, those two periodic broods — officially known as Brood XIX, the Great Southern Brood, and Brood XIII, the Northern Illinois Brood — will appear at the same time, and in some parts of central Illinois, side by side.

The double rising has not happened since 1803. For some perspective, consider that in 1803 Chicago was not yet a city, just a fort built at the intersection of what is now Michigan Avenue and Wacker Drive.

The rise of the cicada will span 16 states ranging from Oklahoma to Virginia, and some cicadas have already begun to emerge in the South. It will probably start in the Midwest in a day or two. In certain parts of Illinois, scientists say the two broods will be close enough to hear each other sing, a noise level that can roar louder than a jet engine.

While much has been made of the noise level of all those chirping cicadas, some scientists are taking a closer look at the timing of their visit. Thanks to climate change, the cicadas are ahead of schedule.

Emergence depends on a key variable: soil temperature. Cicadas are sensitive and will only burst out of the ground once soil temperatures reach about 64 degrees Fahrenheit about 6 inches deep.

“That’s the magic number,” says Floyd Shockley, an entomologist and collections manager at the Smithsonian National Museum of Natural History.

Stephanie Adams, a scientist at the Morton Arboretum in suburban Chicago, displays a cicada in the palm of her hand.
Juanpablo Rameriz-Franco / Grist

Brood XIX, the largest brood, and Brood XIII, one of the densest broods, have been burrowing through the soil and feeding on the nutritious fluids of tree roots for the past 13 and 17 years, respectively. Now they wait for a deep-rooted, instinctive clock to tell them to simultaneously dig out of the ground.

But that clock can tick faster these days.

“We’re on a steadily warming planet,” and the periodic cicadas know it, according to Shockley. He said the first crickets that emerged this year crawled out in February – which is not entirely out of the norm. There are early birds every year, but this year he said there was an “extraordinarily high number” of coming out prematurely.

“It’s happening earlier and earlier,” Shockley said. “And we think that it’s completely related to the local conditions being just right earlier and earlier because of climate change.”

The soil temperatures when cicadas will begin to emerge typically occur in mid to late May, according to Scott Lincoln with the National Weather Service’s Chicago office. But the average date when soil temperature would prompt the emergence of the cicada has trended earlier over the past 30 years: about six days earlier in one Chicago suburb, and about 10 days earlier further northwest in DeKalb, Illinois.

According to scientists at the Morton Arboretum in suburban Chicago, it’s not just the crickets that are getting ahead of themselves. All kinds of species of trees, shrubs and perennials bloomed unseasonably early this year. Maples, elms and magnolia trees bloomed almost a month early in the Chicago region.

There are nearly 200 species of cicadas in North America, of which only seven exhibit synchronized life cycles of 13 and 17 years—also known as periodical cicadas. These crickets, the longest living of the species, historically emerged in late spring or early summer, compared to the annual crickets that emerge each year near the end of summer. The two never overlap. By the time the annual cicadas come out, the magazines are long dead.

There are currently 15 periodic hatches distributed across the eastern United States, 12 of which are synchronized to a 17-year life cycle and three that are synchronized to a 13-year cycle. Each brood contains a minimum of three or a maximum of four cicada species – each species with its own distinctive tune.

For several weeks, some residents of central Illinois will be able to hear all seven species of cicadas in a single day, according to Shockley.

Some scientists, according to Stephanie Adams with the Morton Arboretum, believe that rare proximity between the two broods may allow species from the neighboring broods to court, mate and possibly reproduce. “There’s curiosity about whether they’re going to hybridize and maybe produce a whole new species, so that’s really unknown,” she said.

A recent one study found that the large number of crickets buzzing in the many forests of the eastern United States can be a feeding sensation for some 80 bird species that cannot be missed. The short-term bump in cicada calories isn’t just good for birds, it’s also a huge boon for the caterpillars, who will get a rare break from their predators.

Two women in caps wrap translucent white tulle fabric around a young tree.
At the Morton Arboretum in suburban Chicago, Rachel White, left, and Rachelle Frosch, on the ladder, wrap a sapling in tulle to protect it from emerging cicadas. A female cicada can damage small trees and shrubs by cutting into the bark while laying her eggs. Juanpablo Ramirez-Franco / Grist

All told: billions upon billions of cicadas will buzz around for four to six weeks, but no one gets hurt – just potentially annoyed.

Cicadas don’t have stingers, they don’t bite, and they pose no real threat to humans. But the insects can damage small trees and shrubs as part of their life cycle. The damage is caused when the female starts laying her eggs: she will cut into the branches of small trees and shrubs to lay up to 600 eggs inside the bark.

The best way to protect vulnerable trees? Run to a fabric store and pick up the nearest bolt of tulle. The idea is to wrap the material typically used for ballet tutus like a lollipop around the tree. The hope is that the fine, lightweight mesh will keep the crickets off and the sunlight in.

But if the thule does not make it in time, the eggs will take six to eight weeks to mature after being deposited in the small branches of young trees, during which the tips of affected branches will turn brown: “It is a natural pruning opportunity,” Shockley said. If they survive, those same trees will be bushier and healthier the following year.

Eventually, the cicada nymphs will hatch, drop into the soil, burrow and start their 13- and 17-year cycles all over again.

“They’re a good barometer for the impact of humans on a species that was here before humans got here,” Shockley said. “And so, looking at those patterns tells us a lot about what impact we’re having on the environment.”

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