What’s that sound driving you buggy? Cicadas

Last week, Jennifer Horn-Frasier was driving on the interstate near Peoria, Ill., on her way back to Iowa City when she heard a faint noise.

“I was like, “I think I hear cicadas,’ so I rolled down my windows, and sure enough, you could hear their distinct buzzing,” said Horn-Frasier, 54. “It was so loud, and this is coming from the interstate, so I can only imagine how loud they were up close.”

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For the last few weeks, billions of periodical cicadas from two broods on different cycles have emerged simultaneously from parts of Iowa and the southeastern United States, which experts say hasn't occurred for more than 200 years.

Much of Eastern Iowa is experiencing the chirping of the typical annual cicada and the Brood 13 periodical cicada, which emerges every 17 years. Southeast Iowa is experiencing both broods — plus the annual cicadas.

Periodical cicadas are split into different broods depending on region and emergence. Parts of Iowa began experiencing the two different broods when soil temperatures reached the mid-60s this spring:

"If people want to come see them, they should do so sooner rather than later because before you know it, they will be gone for another 17 years," said Andrew Forbes, professor of biology at the University of Iowa.

Young cicadas, known as nymphs, spend 13 or 17 years feeding on tree roots and shedding their skin four times. Environmental cues signal when it's time to emerge above ground, where they will shed their skin one last time.

Once free from underground, periodical cicadas mate and lay eggs in tree twigs and stems. Above ground, the adults live only four to six weeks, and the male mating calls echo throughout the region until they attract a female.

The sound of their buzzing can reach over 90 decibels in areas where cicadas number in the millions, Forbes said, which is equivalent to the sound a lawn mower makes or a motorcycle traveling at 30 mph. According to researchers at Purdue University, exposure to this level of sound for up to eight hours can damage your ears.

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After mating, female cicadas lay their eggs. The hatching nymphs burrow underground to repeat the cycle. Annual cicadas can be spotted every year, while periodical cicadas come in waves.

Frances Owen, an education specialist for the Johnson County Conservation Board, said periodical and annual cicadas differ not only in how long they remain underground, but in their size.

"The periodical cicadas are a little bit smaller as adults than the annual cicadas that we see here and in the Eastern U.S.," she said. "The periodical cicadas all have red eyes and are very distinct when you're looking at them."

The periodical cicadas' large-scale emergence is due to an evolutionary strategy. Predators like birds and other insects become indulged to the point where they get sick of eating the cicadas, according to Owen.

Both broods of periodical cicadas can catch the fungal infection massospora cicadina. This fungus eats away at their abdomen, creating spores in which "the infected cicadas fly up high into the canopy, and shake their bodies so these spores rain down onto the forest floor, spreading the fungus to other cicadas," Forbes said.

Owen said the fungus alters the cicadas' brain chemistry, causing male cicadas to mimic the behavior of females and mate with other males. This further spreads the fungus and ultimately leads to their demise. She said the fungus affects only cicadas and is harmless to humans.

"We've found a couple of infected cicadas over the past week, so (the fungus) is here, but we don't know how prevalent it is," Forbes said.

He added, "We're getting towards the end’ of the cicadas emerging and that within a couple of weeks, "you won't notice them as much."

If you want to see cicadas yourself, Owen recommends going to local forests or other wooded areas, such as Kent Park near Oxford and the Cangleska Wakan-Celebration Barn near Solon.

A cicada party

After returning home from her trip, Horn-Frasier got to see cicadas while she and her husband were mountain biking at Sugar Bottom Recreation Area between North Liberty and Solon. She said they stopped near the south section of the bike trail, where they saw an “uncountable” number of cicadas flying around.

“They were camouflaged by the trees’ foliage, but if you looked carefully, you could see dozens flying around in one spot,” Horn-Frasier said. “It’s really cool to be able to witness this natural phenomenon in person.”

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