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The cicadas are coming – We asked an entomologist about it

LANSING, Ill. (May 9, 2024) – It may not be today, tomorrow, or even next week, but Brood XIII is coming soon.

The Lansing Journal talked to Dr. Derek Rosenberger, biology professor at Olivet Nazarene University, about the 17-year periodical cicadas that will soon emerge across northern Illinois. Rosenberger coordinates the zoology program at Olivet, and is an expert in entomology, the study of insects.

Brood XIII every XVII

17 years ago, countless periodical cicada nymphs in northern Illinois — called Brood XIII — took up residence underground. They’ve been feeding on tree roots ever since.

In the next few weeks, the teenage insects will start emerging to feed, mate, lay eggs, and die before the next generation hatches and starts the process all over again.

The scientific community isn’t sure exactly why the insects emerge every 17 years.

“They’re alive all that time, just eating and feeding off the roots of trees,” Rosenberger said. “17-year cicadas are actually mature — they could come out of the ground and molt into adults — after 12 years. So for five years, they’re hanging out underground just kind of waiting. And we still don’t know exactly why that happens, there are still hypotheses that people fight and debate about. But what makes them really cool is that they all come out together after 17 years.”

The group that emerges comprises three different species: Magicicada septendecim, Magicicada cassini, and Magicicada septendecula, according to the University of Illinois.

“They look very similar to each other, but they’re different species. There might be some places in Brood XIII where there’s a whole lot of one species and not very many of the other two species. You can actually tell the difference with their songs,” Rosenberger said.

For the first time since 1803, Brood XIII and Brood XIX are emerging the same year. Brood XIX are 13-year cicadas, and although it’s significant that both broods are emerging at roughly the same time, they won’t overlap geographically. Brood XIII is emerging in northern Illinois, while Brood XIX is in primarily in Illinois’ southern half.

What will the cicadas be doing in Lansing?

The insects will emerge once the ground they’re living in — 8 inches below the surface — reaches a temperature of 64 degrees.

“In some places, there’s going to be a lot of them coming out, and in some places you won’t even know there’s an emergence happening. I don’t know how Lansing’s going to be. In more urban areas, there tend to be fewer of them.”

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After molting, the 17-year cicadas will appear white for a short period of time, before their new form hardens. (Photo: Bill Nino on Unsplash)

Both males and females emerge, and as they climb nearby trees, they will molt, and leave behind a shell, which is familiar to many. As the adults emerge, they are white and soft for a few hours before they harden, usually overnight.

“It’s called ecdysis when they emerge out of their nymphal skin as an adult,” Rosenberger said. “Anytime an insect emerges from an earlier instar (a developmental stage), they break open their skin, they take in air and kind of fill up like a balloon, and their exoskeleton hardens larger.”

Soon after, treetop serenades will begin, as the male cicadas sing to attract a mate. Once mating is complete, females will lay their eggs (called ovipositing).

“They’ll lay their eggs in one branch. They’re able to inject those eggs into the branch, and that can result in that branch being killed, but not always. It just kind of depends on how many and how bad the scar is,” Rosenberger said.

The parent cicadas are alive for about five weeks, and then they die and fall to the ground, where they serve as a valuable boost of nitrogen fertilizer for trees, Rosenberger said.

Six to ten weeks after the eggs are laid, they will begin to hatch, and the little cicada nymphs will find their way to the ground and begin to burrow down 8–12 inches, where they will begin their 17-year-long graze of tree roots.

How will the cicadas affect life in Lansing?

The effect will be relatively minimal, but Lansing residents might notice the following:

Sound: If you live in a high-density area, the male songs will get quite loud during the peak mating period.

Droppings: Yes, after cicadas eat, they poop. Rosenberger said cicada defecation will look like “little droplets of water.”

Odor: Many residents won’t notice an odor at all. In high-density areas, however, as the cicadas die and decompose, an odor may be noticeable.

Do they bite?: Cicadas do not bite or sting.

Effect on trees: The highest-density areas of cicadas are typically ones that have a large number of old trees. When cicadas surgically insert their eggs into tree branches, sometimes weaker branches fall, effectively trimming the tree.

“They’re really good for older trees because they’ll prune them. There have been reports of trees that had a lot of cicada eggs laid in them, that next year they flowered really well,” Rosenberger said.

For smaller and newer trees, however, the egg-laying can cause harmful damage, and residents may want to take steps to protect their trees. The College of Agricultural, Consumer, and Environmental Sciences at the University of Illinois has a list of steps to take to protect small trees: extension.illinois.edu/blogs

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A young tree on South Schultz Drive is protected with a mesh covering designed to deter cicadas. (Photos: Melanie Jongsma)

Effect on animals: Rosenberger said cicadas have no significant impact on pets such as dogs and cats. The impact they have on other animals, however, is a positive one.

“It’s fantastic for wildlife,” Rosenberger said. “Because cicadas are emerging during [bird] nesting season, these birds are looking for insects. Even if it’s a bird that for the rest of the year might eat seeds from your bird feeder, during the spring, most birds are eating insects. And most birds are trying hard to find enough insects to feed their young, and not finding enough. So during years with cicadas, most of the nestlings survive, so you actually get these bumps in bird populations.”

Stay updated on a special occurrence

Rosenberger and his students will be traveling around Illinois in the coming weeks to attempt to gather samples of the various periodical cicadas species — both in Brood XIII and XIX.

He recommends Lansing’s amateur entomologists download an app called Cicada Safari, which allows users to track cicada sightings, log their own photos, and learn more about the emergence.

“This year we had an eclipse, we have the double brood cicada emergence in Illinois, out east, there was that earthquake. We have all of these natural things that are happening, and it’s giving people an opportunity to come together over nature,” Rosenberger said.

For more information on the cicada emergence in Illinois, visit extension.illinois.edu/blogs

Josh Bootsma
Josh Bootsma
Josh is Managing Editor at The Lansing Journal and believes in the power and purpose of community news. He covers any local topics—from village government to theatre, from business openings to migratory birds.

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