Billions of periodical cicadas to swarm 15 states in coming weeks

It’s a debut that was 17 years in the making, and in a matter of weeks, it will grab the attention of millions of Americans.

Billions of periodical cicadas will emerge across 15 states and Washington, D.C., with some possibly coming out as early as late April or the first week of May, said Gene Kritsky, a periodical cicada expert and dean of Behavioral and Natural Sciences at Mount St. Joseph University in Cincinnati.

This year’s group, known as Brood X, is the largest of the 17-year-broods in both density and geographical area. And while the name may sound dramatic, the “X” is just the Roman numeral 10 in this instance, Kritsky said.

Here are some of the most common questions surrounding these large, redeyed insects:

● Where will the Brood X cicadas emerge?

This large emergence will affect the District of Columbia and at least parts of these 15 states: Delaware, Georgia, Illinois, Indiana, Kentucky, Maryland, Michigan, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Tennessee, Virginia and West Virginia.

There are three major patches where you’re likely to see the largest swarms of these cicadas, Kritsky said:

● The southeast corner of Pennsylvania, almost all of Maryland, parts of Delaware and New Jersey, and a few areas in New York.

● Ohio, almost all of Indiana, a few areas in eastern Illinois, and northwestern and eastern parts of Kentucky.

● Western North Carolina, east Tennessee and a scattering around west Tennessee and the northern part of Georgia.

● When are the cicadas coming? When soil temperatures hit 64 degrees a few inches below ground, the cicadas will start to emerge. That usually comes on the first or second day when temperatures reach the low 80s, Kritsky said.

“It’s hard to make predictions other than just (looking at) long-term climate trends,” Kritsky said. But generally, those temperature markers come earlier for Southern states. So northern Georgia could see the right conditions for Brood X emergence around the first part of May, while Cincinnati could reach that point around mid-May.

But Kritsky said Brood X areas that see an unseasonably warm April could see the cicadas earlier than in past years.

● How loud can a swarm of cicadas get?

While doing quadrant studies under a large oak tree, Kritsky estimated thousands of cicadas in the surrounding area. Standing a few feet away, he measured the insects’ sound at 96 decibels, higher than a low-flying airplane, which can hit about 80 decibels.

“These individuals will crawl out every 17 years and they know they have only one purpose, and that is to mate and reproduce,” said Jerome Grant, a University of Tennessee entomologist. “So they’re going to make a lot of noise to attract females to mate.”

Competitive males are all about flexing their muscles. That’s how they make their trademark catcalls, Grant told the Knoxville News Sentinel, part of the USA TODAY Network. Male cicadas have a ribbed organ called a tymbal. When they flex their muscles, the ribs rub together and produce sound.