Maybe you’ve noticed some little cicada-like creatures on the ground while gardening or after flipping over a log lately.
That’s because the brood of cicadas that emerge from the ground every 17 years in northern Illinois is preparing to make its appearance, experts say.
The nymphs are the immature stage of life in which cicadas spend about 17 years underground feeding off the sap of tree roots. And they’re starting to dig tunnels to reach the surface.
“They are preparing to emerge,” said Negin Almassi, a resource management training specialist with the Cook County Forest Preserve District. “I have not seen any reports, nor have I myself seen any adults yet. The soil is not warm enough yet for that.
“It’s a fun wait-and-see game right now to see when the firsts start to emerge, so they’re getting ready, and they generally do that about three weeks before they start coming out.”
The periodical cicadas should start to appear once the soil reaches 64 degrees, which is expected by late May.
Once emerged, the nymphs will shed their exoskeleton and the billions of male cicadas across the state will loudly “sing” to attract a mate. The cicadas, which live about 10 days, then breed and lay their eggs in the bark of small trees. About six weeks later, the nymphs hatch from the eggs, fall to the ground and burrow beneath the surface where they’ll spend the next 17 years.
Months after the 17-year cicadas have come and gone, people across Chicago and the rest of northern Illinois will again hear more cicada buzzing. That will be from the male annual cicadas that fill trees in the region every year in late summer. The annual cicadas arrive in August and September and aren’t expected to overlap with the 17-year cicadas.
In central and southern Illinois, another breeding group of cicadas that arrive every 13 years are expected to emerge in the next couple of weeks. Some areas of central Illinois could see a mix of the 13-year and 17-year cicadas — a phenomenon that hasn’t been seen in 221 years.
Almassi, who helps run the forest preserves’ singing insect monitoring program, is heading an initiative for this year’s cicada arrival to encourage people to record videos of the insects using the iNaturalist phone app. She said there also will be monitors installed throughout the forest preserves to “give us a better sense of how numerous they are in different places.
“The really interesting thing about recording is that, when scientists like myself go to listen to them, we can tell is it a chorus, is it just one individual male singing, or is it a pulsating chorus where you have a number of males that are now generating enough noise to attract females,” Almassi said.
This year’s cicada phenomenon also presents scientists with opportunities to learn about soil environments and use what they learn to study the ways past land management has affect the ecosystem in areas where cicadas don’t emerge.
Cicadas “tell us about what’s happening in the soil,” Almassi said, calling them a “window” into the soil environment. “So, if we have a healthy population of cicadas emerging … that tells us that that habitat has been healthy enough for the last 17 years to sustain their population.”
Netting can protect young or small trees from cicadas
The periodical cicadas, like the yearly ones, aren’t invasive and don’t hurt the ecosystem. But their egg-laying can damage trees and plants. That’s why the Morton Arboretum in Lisle has put out netting to protect hundreds of its trees.
“The female cicada has a specialized organ called an ovipositor that will cut into branches like a pocketknife and deposit her eggs inside of the bark, and that can cause branch death or dieback,” said Stephanie Adams, the arboretum’s plant health care leader.
Cicadas seek young or especially small trees for their egg-laying and also wooded shrubs. The twigs they choose usually are one-eighth to half an inch in diameter.
“If you have a preferred host that you just planted in the last few years, and it’s still a pretty small tree, you might want to consider protecting it,” Adams said.
You could wrap a tree with a netting with holes that are a quarter of an inch or less wide. The tree should be wrapped by early May, after leaves develop but before the cicadas arrive, and the netting should be left on for about six weeks.
“With enough branch damage, that basically cuts off sap and water movement within the tree, which prevents photosynthesis,” Adams said. “And, if there’s not enough photosynthesis for the tree to maintain its leaves, then it will die.”
Almassi said people should avoid sprayingy pesticides on cicadas or lawns.
“This is a really cool natural phenomenon, and you don’t want to poison yourself or the many things, from dogs to birds, that eat the cicadas,” she said. “It’s only going to do them and the ecosystem more harm than good.”
