A 'Tsunami' of Brood X Cicadas Is About to Hit the U.S.—How to Check When They Will Come Out

A "tsunami" of cicadas will emerge from a 17-year slumber in more than a dozen states across the U.S. in the coming months, with billions of the insects surfacing from the earth to conduct a "boisterous" mating ritual.

The swarms, collectively "Brood X," are periodical cicadas that have spent almost two decades preparing for the flight, which will see them mate and lay eggs before dying—enjoying a short burst of life before the hibernation process starts anew.

They will emerge in Delaware, Georgia, Illinois, Indiana, Kentucky, Maryland, Michigan, North Carolina, New Jersey, New York , Ohio, Pennsylvania, Tennessee, Virginia, West Virginia, and Washington, D.C., researchers have said.

The three species that make up Brood X will surface from the soil between May and late June. Periodical cicadas are found nowhere else on the planet except the eastern half of North America, with the last emergence event taking place back in 2004.

That's according to Michael Raupp, Professor of Entomology and Extension Specialist at the University of Maryland, who told Newsweek there are several key signs to look out for that could indicate the insects are about to make an appearance.

He said the cicadas will start to make "exit tunnels" in April so people can look for holes in the soil around trees that are about the size of a dime. Typically, small "mounds or turrets" on the ground will mark where Brood X cicadas will emerge. "If you had cicadas in your yard in 2004, you are very likely to have them this year," he said.

It's not a random event, either. Experts at the University of Connecticut have compiled a detailed map of locations where the insects are expected to appear in the U.S.

"Here in Maryland the vanguard will appear in early May with the cicada tsunami hitting in the last two weeks of May," Prof. Raupp explained via email.

"They will appear in the southern portion of their range a week or so earlier depending on weather conditions. They are as reliable as Halley's comet or Washington's cherry blossoms, a 100 percent guarantee Brood X cicadas will appear."

The professor said one big cue for the emergence is when the soil hits about 64 degrees Fahrenheit at a depth of eight inches. That signals to the cicadas the ground is warm enough for them to thrive—flying to treetops, drinking sap and mating en masse.

Cicadas are well-known for "singing" during daylight, as males synchronize noises in an effort to attract the females. The adults have a lifespan of about four weeks.

"Of the fifteen broods of periodical cicadas that emerge every 13 or 17 years, Brood X, set to appear this spring, is the most widespread of all," Prof. Raupp said.

"Periodical cicadas will emerge in 15 states and the District of Columbia. This means that billions of cicadas will intersect with tens of millions of people in major metropolitan centers. In cities and suburbs, children of all ages will have an unparalleled opportunity to witness and enjoy one of Mother Nature's most unusual and fascinating events."

He said those that emerge from the soil and survive the immediate threat of predators will "join brood-mates in a boisterous assembly, the cicada mating game."

"After mating, females deposit eggs in the tips of tree branches, then billions of adult cicadas will die and fall to the ground. After several weeks, eggs hatch and tiny cicadas tumble to the earth and enter the soil to find tree roots on which they will feed for the next 13 or 17 years, thus completing the circle of life," the professor said.

"Birth, death, songs, romance, sex, predation, murder and mayhem, the appearance of Brood X will be like having a BBC or Nat Geo documentary in your backyard."

A newly emerged adult cicada suns itself on a leaf May 16, 2004 in Reston, Virginia. After 17-years living below ground, billions of cicadas belonging to Brood X will emerge across much of the eastern United States. The cicadas shed their larval skin, spread their wings, and fly out to mate, making a tremendous noise in the process. Richard Ellis/Getty Images