They're here: Cicadas emerge in Chicago area, earlier than usual

Listen closely, Illinois: They're here -- and they're about two weeks early.

Of course, we're talking about 17 and 13-year cicadas set to emerge in Illinois mid-May and early June, with Brood XIII in Northern Illinois and Brood XIX in southern Illinois. In a small part of the Chicago area, both will emerge at the same time, experts say.

In some parts however, an early emergence has already begun.

"The periodical cicadas have been emerging for the last week and a half," Stephanie Adams, Plant Pathologist at Morton Arboretum in Lisle said Tuesday of Brood XIII, which will soon overspread across the entire Chicago area. "We found them both out here in our landscape and also in our East woods."

According to Adams, the emergence of the first cicadas comes about two weeks ahead of the historic average. It will continue to be sporadic, as soil temperature, mulch and turf grass all impact cicadas differently. For example, the soil is warmer near pavement, so cicadas in the those spots are expected to emerge quicker.

"Anything in biology always has a gradient," Adams continued. "So you always have early emergers and then you have ones that will emerge kind of late."

Overall, the cicadas will be emerging through mid-June, Adams said. Between five and 10 days after they crawl out and is when the males will start to sing, Adams added.

"The noise you actually hear is from the male cicada," Adams said. "He has a drum-like organ on his stomach that makes noise that attracts the females, and so we'll start hearing that probably in the next two weeks or so."

Earlier this month, the city of Chicago issued an advisory alerting residents that cicadas from Brood XIII are expected to surface in the Chicago area around late April or early May, lasting through early June. The northern suburb of Lake Forest issued a similar timeline, saying "cicadas will be emerging in April/May/June, depending on weather conditions."

For weeks, environmental clues have pointed to a potential early emergence. Experts say residents can look to nature for a clearer answer.

"Research shows that the particular night of the periodical cicadas’ emergence depends on soil temperature," a post from the National Weather Service said. "Cicada juveniles, or nymphs, emerge after a rainstorm when the soil temperature at 8 inches in depth exceeds approximately 64°F."

Allen Lawrance, associate curator of entomology at the Peggy Notebaert Nature Museum in Chicago, said typically, periodical cicadas emerge in mid-May. Warmer weather could push this timeframe earlier, Lawrance said, but only if it's enough to push soil temperatures above the 64 degree threshold.

"A warm rain at the right time will often kick off their mass emergence," Lawrance said. "So we will have to see."

According to the NBC 5 Storm Team, the next chance of rain for the Chicago area comes Thursday.

In southern Illinois and Missouri however, where Brood XIX will pop-up, there are other signs.

"The 13-year periodical cicadas of Brood XIX may emerge a little earlier," Lawrance said. "Across parts of their range further south they typically begin emerging in mid-April."

Lawrance added that some have already reported seeing adult cicadas in Georgia and the Carolinas, but that "the floodgates have yet to open."

One report from NBC Affiliate KSDK in St. Louis noted that the blooming of certain flowers tend to coincide with an emergence, and that the weather was ripe for cicadas to potentially come out early. However, a recent cold snap foiled those plans.

Whether or not they come early, some parts of the cicadas will stick around longer than their lifespan, which is approximately four to six weeks, experts say.

"Adult cicadas will be active until mid- to late-June, but you will see evidence long after they are gone, including their wings, molts, and decomposing bodies," cicada expert Catherine Dana, an affiliate with the Illinois Natural History Survey, told NBC Chicago. 

Where will cicadas emerge in Illinois?

Here's a map of what to expect in Illinois, according to data from the USDA Forest Service.

"Most of the state of Illinois will experience periodical cicada emergence in 2024," the University of Illinois reported.

The Northern Illinois Brood itself is huge, with a reputation for the "largest emergence of cicadas anywhere," according to the University of Illinois.

In 1956, entomologists reported as many as 311 "emergence holes" per square yard in a forested floodplain near Chicago, which experts say translated to 1.5 million cicadas per acre, according to the University of Illinois.

"When the cicadas start dying and dropping from the trees later in the spring, there are large numbers on the ground, and the odor from their rotting bodies is noticeable," the U of I reports. "In 1990, there were reports from people in Chicago having to use snow shovels to clear their sidewalks of the dead cicadas."

Which areas will see the most?

According to Lawrance, cicada distribution will be patchy.

"Not every neighborhood is going to be as dense with them as others," he said. "One area may be slightly more quiet, and you'll hear them in the distance. And then you go to the next neighborhood, and it's hoppin', and they're everywhere."

There is one determining factor, however: If they were there before, they'll be there again.

"So, which neighborhoods you would expect to find them in will depend on where they were last time they emerged," Lawrance said. "If the soil had been completely dug up and replaced due to construction, there may be fewer cicadas there. But if they were there last time, chances are, they'll still be there."

The same goes for the next 17 years.

Why cicadas are beneficial

According to experts, the cicadas are a good thing for the ecosystem. They are a valuable source of food for insects, birds and other predators, and they can help aerate lawns. The Environmental Protection Agency notes cicadas are a good source of compost, providing nutrients to the soil as they decompose.

"All the animals that are around when they emerge are going to be very full and happy," Lawrance said. "Plants are going to get a boost in fertilizer for a little bit...when we have extreme weather events, like a drought, that cicada emergence happens at the right time that can provide a really valuable food source when nutrients are very scarce."

Still, there's going to be a lot of them, Lawrance said, especially on and around trees, where "piles" of cicada shells can are expected after the insects have "feasted" on fluid from branches and woody shrubs. One article from the University of Illinois Extension stated that Brood XIX has a reputation for being the "largest emergence of cicadas known anywhere," due to the brood's size.

'There's no stopping them'

According to the Environmental Protection Agency, pesticides are "generally ineffective at keeping cicadas away."

"So many cicadas emerge at once that more will inevitably move in," the agency said. "Spraying also doesn’t make sense because cicadas are generally harmless. Applying pesticides to control cicadas may harm other organisms, including animals that eat cicadas."

With such a large number, there will be no where to run come June, Lawrance stressed.

"There's no stopping them. They're here. It's temporary, and there's really no escaping them," he said.