Millions of cicadas will flood Eastern Iowa this spring

The chorus of cicadas — a cacophony of rhythmic zings and high-pitched chirps — is a normal part of Iowa’s summer soundtrack. This year, their song may grow even louder when more members join the ensemble.

For the first time in more than 200 years, two broods of periodical cicadas will emerge from Iowa soils — and beyond — at the same time, said Zach Schumm, an insect diagnostician at Iowa State University’s Plant and Insect Diagnostic Clinic.

“This is a really weird phenomenon that we only get to see a few times in our lives,” he said. “It's like seeing a really cool comet in space that you only get to see every 70 years.”

Cicadas are insects with long, beak-like sheaths used to feed on plants. They can grow up to 2 inches long, and males are known for their loud mating calls.

Annual cicadas can be spotted every year. Periodical cicadas, on the other hand, come in waves.

Young cicadas, called nymphs, feed on roots and organic material underground for 13 or 17 years, depending on the species and their life cycle. Environmental cues, like soil temperatures, alert them when it’s time to emerge in mass droves and reproduce above ground.

Once free from the earth, periodical cicadas will then mate and lay eggs in tree twigs and stems. The nymphs that hatch will then burrow underground and start the cycle again.

“The eastern part of the United States is the only region of the entire world that has these periodical cicadas,” Schumm said. “We're quite lucky to experience it.”

Periodical cicadas are split into different broods depending on their region and emergence timing. Iowa will see two broods emerge this spring when soil temperatures get above the mid-60s:

Eastern Iowa, particularly Southeast Iowa, would experience both broods this year as well as annual cicadas, Schumm said. Actual distributions vary year to year, though, and are hard to predict.

“If you're in the right area, you can see and experience millions upon millions of cicadas... Certain areas are definitely going to be drowned out by the noise,” he said. "Other areas, even within the range, you might not really find many at all. But odds are you're probably going to see or notice some.”

Cicadas don’t harm humans or agricultural crops. Laying their eggs in trees can lead to flagging, when the tips of branches are damaged and leaves turn brown. Flagging doesn’t typically cause long-term harm to otherwise healthy trees, but if the plants are already affected by drought or disease, it can increase risk of tree death, Schumm said.

Cicada abundance will likely peak in Iowa around May. The adult insects live only four to six weeks, their mating calls reverberating throughout the region until they lay their eggs.

“Those two broods aren’t going to align again for another couple hundred years,” Schumm said. “Because they're harmless and they're not really going to hurt anything, it's better to just enjoy it, observe it and be fascinated by it.”

Brittney J. Miller is the Energy & Environment Reporter for The Gazette and a corps member with Report for America, a national service program that places journalists in local newsrooms to report on under-covered issues.

Comments: (319) 398-8370; brittney.miller@thegazette.com