An insect often touted as one of North America’s most fascinating is now making its first appearance in this area in 17 years.

In fact, with populations that can reach 1.5 million insects per acre, it could be said that the periodical cicada is taking central Iowa by storm.

Their 17-year lifespan puts periodical cicadas among the longest-lived insects in the world, said Iowa State entomology professor Donald Lewis.

Best known for the uniquely buzzing “singing” sound created by the males of the species, the emergence of periodical cicadas every 17 years is descried by Lewis as “an incredible event — a phenomenon that truly exceeds the imagination of science fiction.”

Though admittedly biased toward most any insects, Lewis said that the cicada emergence is something so fascinating it transcends the realm of science into something that is interesting to the general public.

The “singing,” which is done by the males to announce themselves to the females, is created when strong muscles vibrate two shell-like membranes located along the sides of the abdomen, Lewis said. As the drum membranes vibrate several times each second, high-pitched, rapid clicks resonate through air sacs and structures that control the volume and quality of the sound.

The sound increases further due to the upward angles of the wings, creating a megaphone-like chamber that amplifies the sound, Lewis said.

“When you realize that cicada populations can average from 20 to 40 thousand per tree,” Lewis said, “it’s easy to see how their sounds can be as deafening as they are incessant.”

The cicadas spend 17 years as nymphs embedded 18 to 24 inches deep in the soil of forested and wooded areas, Lewis said. During that time, the insect nymphs feed on the sap from tree roots.

The nymphs then emerge from the ground all at once in a “highly synchronized fashion,” digging their way out of the soil during late May and June and climbing up tree trunks, poles and posts, Lewis said.

The winged adult cicadas then emerge from the nymph’s outer shell within about an hour, and the fully-formed adults then crawl up onto tree limbs and branches.

Compared to the many years spent underground, the adult phase of life for cicadas is quite short.

In fact, adult cicadas only live for five or six weeks, during which time the insects mate and the females lay eggs upon small twigs of trees and shrubs.

The periodical cicadas can only be found in North America east of the Rocky Mountains, Lewis said. Best areas for experiencing the cicada phenomenon this year in central Iowa include Ledges State Park, the Iowa Arboretum and the Saylorville Lake area.

Strangely, downtown Des Moines near the art gallery is also a major cicada hot spot this year, he said. “There are so many cicadas in that area that the people who live near there are really being driven nuts.”

Lewis said that the exact areas of cicada emergences always vary greatly. Because of the spotty nature of the outbreaks, it takes both planning and patience to witness the phenomenon.

Still, Lewis definitely recommends seeking cicadas out to experience what he fondly calls “the trill of a lifetime.”

“Enjoy the show now,” Lewis pointed out, “because you won’t get another chance until the year 2014.”