Two broods of cicadas are set to emerge in Illinois in late May and June, setting the stage for billions of the insects to buzz across the state.
According to experts, some cicadas could even start to emerge early.
"It's possible," Allen Lawrance, associate curator of entomology at the Peggy Notebaert Nature Museum in Chicago, said, of periodical cicadas potentially coming out ahead of schedule. "These are big populations of cicadas. Given their huge numbers there are bound to be at least a few individuals emerging early regardless, but weather can play a role."
Soil plays a role, too.
According to the National Weather Service, the emergence is dependent on soil temperature.
"Research shows that the particular night of the periodical cicadas’ emergence depends on soil temperature," an NWS post read. "Cicada juveniles, or nymphs, emerge after a rainstorm when the soil temperature at 8 inches in depth exceeds approximately 64°F."
Earlier this week, the Chicago area saw two 80-degree days. Prior to that, the region had seen above average temperatures, and more rainy days in April than dry ones, the NBC 5 Storm Team said.
As of Friday, April 19, soil temperatures were in the upper 40s to mid 50s, NBC 5 Meteorologist Kevin Jeanes said. According to Jeanes, the weekend forecast called for dry conditions and temperatures on the cooler side, with areas of patchy frost through Sunday.
That means in Northern Illinois, the soil temperature still isn't quite right for Brood XIII cicadas to emerge. In southern Illinois and Missouri however, where Brood XIX will pop-up, that may not be the case.
In Missouri, where strong storms last week soaked the ground with warm rain, soil temperatures could rise and push past the 64-degree mark, according to a report from NBC Affiliate KSDK in St. Louis.
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Another sign that could lead to an early emergence, KDSK said, is how early certain flowers bloom.
"The emergence of the purple flowers tends to coincide with the cicada emergence," the report said. "The Missouri Botanical Garden said some of the garden's irises bloomed as early as April 10."
How early could cicadas emerge in the Midwest?
According to Lawrance, the 17-year cicadas -- Brood XIII, which will emerge all across Northern Illinois, including the Chicago area -- are expected to emerge around 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."
Tuesday night, rain is headed to the Chicago area. High temperatures are expected in the mid 70s, with even warmer readings to the south, the NBC 5 Storm Team said. Areas closer to the lake will remain in the 60s.
As of Tuesday, there have not been any documented reports of adult periodical cicadas emerging in Illinois, Lawrance said, adding that some online reported seeing nymphs. While nymphs underground often surface "momentarily" before they burrow up, they do not make loud sounds, Lawrance said.
In Chicago officials, issued an advisory last week, saying the first emergence is expected sometime around late April through early June. The advisory also said that neighborhoods and areas with older homes could see a bigger impact.
In suburban Lake Forest, officials said "cicadas will be emerging in April/May/June, depending on weather conditions."
When it comes Brood XIX the 13-year periodical cicadas set to emerge in the central and southern part of the state, cicadas could surface even sooner.
"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."
Whether or not they come early, some parts of the cicadas will stick around longer than their lifespan, 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 the two broods be seen?
The Northern Illinois Brood, or Brood XIII, will be most seen in parts of northern Illinois and Indiana, and possibly even in Wisconsin, Iowa and parts of Ohio. This brood will be the most prominent in the Chicago area for the upcoming emergence, experts say. But 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."
Meanwhile, Brood XIX, or the Great Southern Brood cicadas, have a more widespread population, covering parts of Missouri, Illinois, Louisiana, North Carolina, Virginia and Maryland.
"Brood XIX is arguably the largest (by geographic extent) of all periodical cicada broods, with records along the east coast from Maryland to Georgia and in the Midwest from Iowa to Oklahoma," the University of Connecticut reports. "Although 13- year cicadas are generally considered to have a southern distribution, the northernmost known record of this brood is in Chebanse, IL, roughly 75 miles from Chicago’s Loop."
While the two broods have different emergence regions, there could be some locations that see an overlap of both.
"Somewhere around Central Illinois, probably like around Springfield, is what some researchers are predicting we may see some overlap of these two ... different broods," Dana said. "It's not going to be a large area. But there will likely actually be some mating happening between these two broods, which is going to be really exciting."
What are the cicadas doing underground?
For the past 17 years, billions of cicadas from Brood XIII have been living underground, tapping into fluid from plant roots, Lawrance said. Once they emerge, they'll be around for between four and six weeks, Lawrance added.
How and when they emerge in such a harmonious way, though, is a bit of a puzzle.
"That's kind of a big mystery," Lawrance said. "How are they so synchronized to do this? At the same time? There seems to be something that's genetically or physiologically controlled, so they just know instinctually to do this."
And once they burrow up, there's "really no escaping 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.
"You're just going to see them sort of flying around, hanging out on trees, and you're going to hear them wherever you go," Lawrance said.
That is, until they die and get composted back into the ground. Or get eaten.
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"Everything eats them," Lawrance said. "The periodical cicadas' 'life strategy' is by emerging all at once. Everything that eats them can eat as many as they want, and there are still more than enough cicadas left behind to continue the population."
Periodical cicadas, Lawrance said, are a "petty tasty snack" to squirrels, birds or snakes. Dogs can eat them too, Lawrance added, in moderation.
"As far as insects go, they're very large and meaty," Lawrance said. "They have a lot of nutrients there."
What exactly are we supposed to do with them?
Not much, Lawrance said.
"You should definitely not try to remove them from an area with billions," he said, adding that they'll get composted back into the soil on their own.
"That's kind of the great role they play within our ecosystems, is they spend a lot of time concentrating nutrients from a really good food resource that is the xylem and plants," Lawrance said. "And then, when they emerge en mass, they return those nutrients to the soil in one big group."
Those nutrients could result in a "big boost" in plant growth over the next couple of years, Lawrance added.
"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."
According to Lawrance, those nutrients could also be used in home gardens.
"If you want to fertilize your garden, or save on fertilizer for your garden, you could just throw some piles of cicadas in there as they decompose," Lawrance said.
'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.
