Some cicadas come every summer, announcing their arrival with a high-pitched hum during Fourth of July parades, backyard barbecues and late-night bonfires.
This year, Brood XIII, a species of cicadas that only appear every 17 years, are returning to Oak Park and other communities in northern Illinois, southern Wisconsin and northwest Indiana this spring.
These cicadas live underground until their 17-year cycle is up. Many will crawl out from underground around May and early June, when the soil is 64 degrees at a depth of 8 inches. They’ll be around for about four to six weeks.
Scientists don’t know how these cicadas know when 17 years are up. But the theory is that they have an internal clock that tracks the life cycle and chemical changes of tree roots around them, according to The Morton Arboretum.
Cicadas that emerge yearly normally come out in late July and August. Periodic cicadas have a black body, orange or red wings and red eyes, according to The Morton Arboretum.
In forested areas, there will be about 1.5 million of these cicadas per acre, according to The Morton Arboretum. Oak Park will likely have less since it’s a more developed and populated area. New construction since 2007, the last emergence of periodic cicadas, could have disrupted the soil, too.
Most of these cicadas will only fly, at most, a half of a mile in their lifetime, said Grant Jones, the village’s forestry superintendent. That means their odds of coming from forested areas or other communities to Oak Park are low.
Jones said when speaking with residents who lived here the last time these cicadas emerged 17 years ago, they said Oak Park definitely had less emerge than in neighboring communities.
Cicadas are not harmful to humans as they don’t bite or sting. But they can produce a lot of noise residents are likely to notice this spring. This sound is male cicadas’ mating call to attract female partners.
“A lot of people are paying attention and kind of curious about cicadas,” Jones said. “People are usually not used to them being around.”
These insects won’t chow down on trees, but they will drill into smaller branches to lay eggs and continue their legacy. This, unfortunately, can cause small branches to break off or die, Jones said. Trees with a trunk less than two inches in diameter and few branches are likely at the most risk.
“Their main purpose is to reproduce and get the next generation going,” Jones said.
These cicadas typically lay eggs in oak, maple, hickory, apple, birch, dogwood, linden, willow, elm, ginkgo and pear trees, according to The Morton Arboretum. They may also lay eggs in shrubs.
The Oak Park parkways have a total of more than 18,000 trees, Jones said. These trees are mostly larger than cicadas can damage. Tips of branches could be affected, but the trunks are generally too large, Jones said.
Residents worried about protecting their trees can protect it with mesh netting to prevent cicadas from drilling into their plants. The netting should have holes no larger than a fourth of an inch, Jones said. This type of netting can be found at hardware stores. Some tree owners even use tulle to protect their plants, Jones said. Openings can be secured with staples, string or zip ties.
“If your little finger fits through a hole, it’s big enough to admit a cicada,” according to The Morton Arboretum.
Sprays or insecticides won’t have an impact on cicadas, either. Exclusion through netting is the best way to keep plants healthy from cicadas, Jones said. But cicadas aren’t the only thing that can potentially damage plants.
“As we get into the heat and often times, dryness, of the summer, that’s another good time to make sure that you’re watering your plants properly just to keep them healthy,” he said. “That way, if there is any damage, they’re not also being stressed by a lack of moisture.”
Others might want to wait to plant smaller trees until the cicadas are gone again.
When removing netting, residents should be sure to do so carefully, Jones said. Branches and leaves can get intertwined and damaged easily during this process.
One common question, Jones said, is if pets eating cicadas could be dangerous. Cicadas are not harmful or toxic to pets, he said, but if a pet eats too many, they might get a stomachache.
After the cicadas mate and lay eggs, they will die. According to The Morton Arboretum, “there will be dead cicadas everywhere,” so residents can expect to see them walking or driving around. As they decay, there may be an odor.
