Since 1997, billions of periodical cicada nymphs have been living underground in total darkness, sucking nourishment from tree roots and counting ever so slowly to 17.
Now their precisely predictable, amazingly synchronized emergence — the state’s biggest insect show of the decade — is underway in several Eastern Iowa counties.
“They are everywhere. It’s unbelievable,” Dave Long, director of the Keokuk County Conservation Board, said Monday.
Donald Lewis, a professor of entomology at Iowa State University, said their synchronized emergence, their 17-year life cycle, their startlingly high numbers and the males’ buzzing chorus combine to leave a deep and lasting impression on human witnesses.
“I can remember growing up, pulling hundreds of their molted exoskeletons off a single tree. It was really cool,” said Johnson County Conservation Director Larry Gullett, who expressed hope that the spectacle will pique an interest in nature for today’s youngsters.
“I was astounded by it the last time it happened,” said Steve Anderson, director of the Washington County Conservation Department.
Keokuk, Johnson and Washington are among 46 Iowa counties in which Brood III of the periodical cicadas are emerging. Other Eastern Iowa counties include Benton, Cedar, Iowa and Louisa.
“It was crazy last week with so many crawling out of the ground. Now they are really starting to sing in the afternoon,” said Neric Smith, a horticulture instructor at Indian Hills Community College in Ottumwa.
The insects emerging now are the offspring of cicadas that emerged, mated, laid eggs and died in 1997.
They have since been living as nymphs beneath the soil, taking nourishment from the roots of trees.
Lewis said the mass, synchronized emergence is an evolved survival trait. Their 17-year cycle keeps predators — raccoons, skunks, foxes, turkeys and crows, among others — from anticipating their arrival, and their vast numbers, coming all at once, create a supply that exceeds demand, he said.
Lewis said the first reports of cicada sightings trickled in from southern Iowa in late May and steadily accelerated. The peak, he said, is likely to be this week and next.
Up to 1.5 million cicadas can crowd into a single acre of woodland, and up to 40,000 in a single tree, a spectacle made even more impressive by the male insects’ distinctive buzzing — a mating call produced by two shell-like drums along the sides of their abdomens.
Though some might find the cicadas a little creepy, they are harmless, according to Lewis.
“They do not damage crops or gardens. They don’t bite. They can’t sting. They don’t invade your house or attack your possessions,” he said.
Within six weeks, the adult cicadas will have mated, laid their eggs and died. When the eggs hatch, the offspring will burrow into the ground where they will start their long, slow countdown to 2031.