One of the most amazing stories of the insect world will unfold this month in southeastern Iowa — including Scott, Cedar, Muscatine and Louisa counties — when the 17-year, periodical cicada crawls out of the ground in woody areas.

Annual cicadas are around every summer. They're the 1- to 1½-inch-long insects that make the high-pitched whining sound you hear incessantly late in the season.

But the red-eyed, 17-year cicada is a particular kind that lives in North America, east of the Rockies, emerging once only every 17 years, in highly synchronized fashion.

The ones we'll see are the offspring of the adults that were last seen in 1997. They laid eggs then, and for 17 years the cicada nymphs have been living underground.

Dr. Donald Lewis, an entomologist at Iowa State University in Ames, received his first call about the emergence Thursday morning from Burlington.

"Cool!" he said in an email announcing the news. "We have waited 17 years for this call."

In Illinois, the affected counties closest to the Quad-Cities are Henderson, Warren and Knox.

People need not be afraid of the cicadas, which live five to six weeks after emerging. Once they're out of the ground, they don't eat anything and they don't bite. The only damage they might cause is some temporary dieback in twigs where their eggs are laid.

They just can be very loud and numerous. 

"With populations that can reach up to 1.5 million insects per acre, the sound (of their singing) can be as deafening, as it is incessant," Lewis said. 

The phenomenon was first studied 1878 by an Iowa State entomology professor.

If you live on land that was originally prairie, be it in town or on a farm now, you likely won't see the cicadas because they live in woods. But in old wooded areas, they'll be difficult to miss.

"You might find them in Duck Creek Park or older parks with undisturbed, old-growth woodlands," Lewis said.

Their "incessant, incredible" singing will be during the day, ending by mid-afternoon or dusk, he said.

The noise is the male cicada's way of attracting a mate. They "sing" by vibrating shell-like membranes along the side of their abdomen several times per second.

The broods stay largely in the same area from cycle to cycle, migrating only about 200 yards at most, Lewis said.

Why the 17-year cycle?

This may have developed over the centuries as a way to escape predators such as birds, Lewis said. With the insects all hatching at once, there are so many of them that they can't possibly be eaten to the point where their existence is threatened.

"It's strength in numbers," he explained.

Lewis finds the cicadas mind-boggling for four reasons: their long, 17-year cycle, their sheer numbers ("They have a population density that is staggering to think of"), their extremely loud "singing" and their exact synchronization.

"They are just bugs after all, bugs living underground, and for them all to emerge at the same time is just amazing."

Hear their sound

You can hear a recording of a periodical cicada chorus online at songsofinsects.com.