Researchers who tracked cicadas 17 years ago wait for return

March 27, 2021 GMT

ALLENTOWN, Pa. (AP) — Seventeen years ago, Rick Crist and Michael Sitvarin put 1,000 miles on Crist’s Jeep Wrangler driving to state parks and municipalities, listening for screams.

The Muhlenberg College undergraduates, equipped with flip phones, paper and pencils, were working on a summer research project alongside their biology professor, Marten Edwards, mapping the places where periodical cicadas had crawled out from the earth to scream, mate and die.

This year, the next generation of those cicadas is set to emerge, and the trio aren’t going to miss the unique, loud, natural phenomenon.


“It’s something, really, just this past week or so, that I’ve started thinking about the cicadas more often, that I have realized that there’s a personal connection,” said Sitvarin, now a biology professor at Clayton State University in Georgia.

“When we were focused on these adults flying around, listening to the mating calls, all of that was so that they could reproduce,” he said. “And what’s going to happen in a month or so is the next generation — that’s the product of everything they were doing. These are their babies.”

What are periodical cicadas?

There are different kinds of cicadas all over the world, said Edwards, who chairs Muhlenberg’s biology department, but the cicadas that emerge every 13 or 17 years can only be found in the eastern United States.

And periodical cicadas are not to be confused with the annual cicadas found in Pennsylvania, Edwards said. While the latter are green, the former are black with orange eyes.

Periodical cicadas live about 10 inches beneath the ground, he explained, tapping into the roots of trees to eat. They start out about the size of a grain of rice, taking 17 years to mature. Then they wait for the soil to become a warm 64 degrees before they emerge, usually around the middle of May.

“That’s why they almost all come out within a few days of each other,” Edwards said. “It’s really incredible how synchronized they are. It’s like, ‘OK, this is our cue, time to come out.’ ”

And once they come out, their entire purpose is to find a mate. The males try to impress females with their screams. The females lay eggs in tree branches that later develop and fall to the ground to start the process all over again. Then they all die.

“So, they’re only around for at most, you know, a month,” Edwards said. “And by July, it’s really hard to find any. By the Fourth of July, I don’t even look for them anymore.”


What’s the noise they make?

Edwards described the cicadas’ mating calls as songs and screams, saying that when they’re all making noise at once, it’s called a chorus. The sound, however, comes from clicking their wings in a special way.

“Essentially, it’s a love song,” Edwards said. “But to somebody who’s unfamiliar with it, it might seem like a scream. Like Metallica is a song to the fans, and it’s a scream to the parent.”

Scientists and researchers drive around state parks and rural areas, listening for the distinct sounds of the three different species of 17-year cicadas.

Edwards says it’s a “magical experience” to hear the cicadas all singing at once, comparing it with seeing thousands of snow geese or a herd of wildebeest.

“Nature is this amazing, powerful force,” he said. “And people come from all over the world to see this.”

And cicadas shouldn’t be a cause for concern, even though some might confuse them for a plague of locusts, Sitvarin said. They don’t bite or sting.

“The adults aren’t out there chewing through crops or destroying ornamental plants or anything like that. Their effects are pretty minimal on the environment,” he said. “Just going out and kind of marveling at them and appreciating that. This is a once-in-a-17-year event, and who knows where you’re going to be in 17 years? Soak it up and enjoy it while you can.”

Where will they be this year?

There probably won’t be any cicadas in downtown Allentown, Edwards explained. And even though a previous map indicted that they were spotted in Lehigh County, it wasn’t detailed enough to show municipalities.

Since cicadas feed off tree roots, they’ll more likely be found in woodsy areas.

“For example, in an agricultural area, where you cleared the land to grow corn or soybeans or some other crops, you’re not going to find any cicadas because the trees have been cut down,” Edwards said. “So you can’t just say because you’re in a rural area, you’re going to see them. And in a lot of suburban areas, there can be lots of cicadas.”

There are theories, too, about why these cicadas only emerge every 17 years.

“The best explanation I know of is that you need to have a lot of them to be able to reproduce successfully,” he said. “ ... If you have a small number of them, they’re not going to be able to reproduce successfully because they’re super tasty.”

Edwards described them as “a big bag of protein.”

“Unless they can come out in large enough numbers, the predators are going to wipe them out,” he said.

How were the cicadas mapped?

The 2004 project was the first time cicadas had been mapped in the state since the 1987 emergence.

“It’s really wild. I mean, it makes you feel a little old, but it’s been 17 years,” said Crist, a genetics researcher at the University of Pennsylvania. “You look back and you think, this had to have been one of the most successful summer research endeavors that you have ever had.”

After driving around the state, Crist and Sitvarin started cold-calling municipalities to see if they had spotted the cicadas. It was very “low tech,” Crist said.

“Our time in 2004 was really the first time applying modern technology and having GPS coordinates and some high accuracy and reliability for this coming summer,” Sitvarin said. “It would be a really nice reference to not just look back at these old crusty papers and try and figure out what was going on, but to say with some precision, they were here last time, are they here now? Or have they expanded farther?”

This year, Edwards is partnering with the University of Connecticut to map the cicadas. They’ve developed an app anyone can use to log sightings.

The mapping is important to compare populations over time, Crist explained.

“Well, I think one of the big things is that humans encroach and the cicadas, while they’re underground, need trees, and they need presumably not polluted land, and like groundwater and stuff like that,” he said.

“So in some ways, it’s sort of a metric of how humans are encroaching on nature, how sort of the suburbs and everything else around southeast Pennsylvania expanding, and also just sort of pollution, runoff, things like that, that would damage their ability to survive for 17 years underground,” he said.

Sitvarin, Crist and Edwards are planning to reunite to see the cicadas emerge.

“It would be so great to have the three of us together again, and do a trip out to one of these big parks and just kind of marvel at the cicadas,” Sitvarin said, adding that there’s a bit of nostalgia involved. “Being able to do that, to reunite and then potentially be there with whatever the next generation of undergraduates are — there’s some interesting parallels there between the next generation of cicadas and the next generation of younger students.”