The sound of cicadas in Illinois is unavoidable every year – but this year might just be a little louder as two broods of cicadas are expected to emerge at the same time this spring and summer.
But what exactly will the volume be?
Let’s break it down.
How many cicadas are expected in Illinois?
According to Dr. Gene Kritsky, dean of behavioral and natural sciences at Mount St. Joseph University in Cincinnati, “cicadas could emerge at densities of up to one and a half million per acre.” And that’s just from the northern Illinois brood, known as XIII, that will emerge in the Chicago area.
Predicting exactly how many can be difficult, cicada expert Catherine Dana, affiliated with the Illinois Natural History Survey, told NBC Chicago.
“Previous research has generally shown that for some of these normal large broods, you can see between 50,000 and 1.5 million cicadas emerge from an acre,” she said.
MORE: When will the cicadas of 2024 arrive and how long will the emergence last in Illinois?
But this will not be the case everywhere.
“You have to keep in mind that they emerge only from under trees,” Kritsky said. “And so, if you’re in a forested area and they’ve already laid eggs there, it could be quite dense. But in many cases, we find that these cicada emergences are relatively patchy. Clear-cutting forests for agriculture, clear-cutting forests for urban development – all of these reduce the cicadas’ egg-laying sites,” he said.
The northern Illinois brood itself is enormous, with a reputation for “the largest cicada emergence in the world,” according to the University of Illinois.
In 1956, entomologists reported as many as 311 “emergence holes” per square meter in a forested floodplain near Chicago, which experts said translates to 1.5 million cicadas per acre, according to the University of I.
“When cicadas begin to die and fall from trees later in the spring, they are in large numbers on the ground and the odor of their decaying bodies is noticeable,” reports the University of Illinois. “In 1990, Chicagoans had to use snow shovels to clear their sidewalks of dead cicadas.”
This could happen again.
“It’s possible because remember that each individual cicada will produce, its nymph skin will be lost, which will accumulate and then as it begins to die after it has finished breeding and laying eggs, it will begin to collect,” Kritsky said. “And we know that people have to remove some of these excess carcasses and shells from their trees, because … after that, after they’re collected from the trees, they can start to smell bad as they decompose .”
Dana added that gutters could also become clogged.
“You might have to take them out of the gutters, you know, we don’t want to clog our gutters,” she said. “A lot of times I see them in piles, you know, with the shells, right? I see them in piles at the base of trees, like just in the corners between the roots. They tend to have a lot of piles . there. But just add them to your compost pile, you know, let them decompose.
What will the volume be?
Although the insects themselves are mostly harmless, their noise can be disruptive. According to the Centers for Disease Control and Prevention, cicadas are among the “loudest insects in the world.”
Each species or brood has its own sound, experts say. Male cicadas can reach decibels similar to a passing lawn mower or jet, experts say. And although their numbers are large, their life cycle is short, only four to six weeks.
“What happens is when you have that many cicadas – even though they are generally quieter than our dog day (cicadas) – all together in one place, it can be deafening,” Dana said.
According to the CDC, sound level meters or smartphone apps have reported cicada noise levels ranging from 90 to 100 decibels, which is “well above” the recommended noise exposure limit of 85 decibels.
Kritsky compared it to a rock concert.
“If you spend any time in a forest of cicadas where they’re just screaming and you get back in your car, you’ll still hear that vibration in your head,” he said. “It’s like going to a rock concert, you’re back in your car and you’re still feeling that music in your head.”
During a full emergence year, when the insects surface, they quickly begin to mate, often resulting in the noise most associated with cicadas.
“Once these cicadas come out of the ground, it’s all about romance,” said Mike Raupp, professor emeritus of entomology at the University of Maryland.
The good news for many is that the noise likely won’t be heard late at night.
“As long as you don’t sleep during the day, cicadas aren’t a problem,” Dana said. “The cicadas will only call when the sun is up, you know, maybe early evening, but usually they will quiet down completely… the cicadas will call quite loudly during the day, but once the sun is up. Come down, it’s over. It’s the katydids calling you and keeping you up at night.
Cicada brood map
For the Chicago area, Brood XIII will be most visible in parts of northern Illinois and Indiana, and perhaps even Wisconsin, Iowa, and parts of Ohio.
Meanwhile, Brood XIX, or 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 (in terms of geographic extent) of all periodic cicada broods, with records along the eastern coast from Maryland to Georgia and in the Midwest from Iowa to ‘Oklahoma,’ reports the University of Connecticut. “Although 13-year cicadas are generally considered to have a southern distribution, the northernmost known record of this brood is in Chebanse, Illinois, approximately 75 miles from Chicago’s Loop.”
Although the two broods have different emergence regions, there could be overlap of the two in some locations.
“It’s like the year of Illinois,” cicada expert Catherine Dana, affiliated with the Illinois Natural History Survey, told NBC Chicago. “We’re going to see cicadas emerge across the state.”
Here’s a map of what to expect in Illinois, according to data from the USDA Forest Service.
“Somewhere in central Illinois, probably like around Springfield, some researchers are predicting that we might see some overlap of these two different broods,” Dana said. “It won’t be a big area. But there will probably be some mating between these two broods, which will be really exciting.”
When will the cicadas emerge and for how long?
The two 2024 broods will emerge earlier than the well-known “dog day” cicadas, which are often seen in early July, according to Dana.
Cicadas typically emerge when the ground begins to warm in spring and early summer.
This means emergence between mid-May and early June, although some could begin as early as late April.
For the Chicago area, Brood XIII will be most visible in parts of northern Illinois and Indiana, and perhaps even Wisconsin and Ohio, in late May 2024, said Dr. Gene Kritsky, dean of behavioral and natural sciences at Mount St. Joseph University in Cincinnati said in a 2023 press release.
According to an article from the University of Illinois Urbana-Champaign Extension, emergence of the northern Illinois brood typically occurs in May and June and lasts about four weeks.
“Adult cicadas will be active until mid-to-late June, but you will see evidence of them long after they are gone, including their wings, molts and decomposing bodies,” Dana said.
What to know about cicadas
Cicadas are not harmful to people or pets, or even home gardens or crops, according to the Environmental Protection Agency.
Cicadas don’t bite or sting, and pesticides won’t work on periodical cicadas, experts say.
“Most of the state of Illinois will experience periodic emergence of cicadas in 2024,” the University of Illinois said. “Besides the noise, which can be significant, this large group of insects is harmless and can be enjoyed and appreciated by nature lovers of all ages.”
Benefits of Cicadas
As for the benefits of cicadas, the EPA notes that they:
- provide a valuable food source for birds and other predators.
- can aerate lawns and improve water filtration in the soil.
- add nutrients to the soil as they decompose.
Life cycle
“During the final molt of their exoskeleton, immature cicadas (i.e., nymphs) construct a tunnel through which they emerge from the ground. They then molt into adults, leaving behind the nymphal exoskeleton, often attached to a tree,” the EPA says. . “Adults climb trees and shrubs and mate. Females deposit their eggs on small twigs (pencil diameter up to ½ inch). Nymphs hatch from these eggs after 6 weeks and drop to the ground They then burrow into the ground and begin feeding on the roots of trees and shrubs to restart the cicadas’ life cycle.
After their appearance, the adults die but leave behind a new generation. These nymphs will live underground until 2038.
NBC Chicago
