CINCINNATI -- They're big, they're loud and they'll fly into anyone who gets in their way.

Cicadas are expected to emerge in Cincinnati this year.

Brood X, a group of 17-year cicadas, isn't due to emerge until 2021. However, some of the brood's cicadas emerged four years early previously, arriving in 2000 instead of 2004, according to Mount Saint Joseph University. The descendants of those early arrivers are expected this year.

The Tri-State will see about 1 million cicadas emerge between May and June, according to Gene Kritsky of Mount Saint Joseph. But that's not much compared to the billion or more expected in 2021.

"That's the big one," Kritsky said. "That's when the 'cicada apocalypse' happens."

In the 2000 emergence, cicadas were seen locally in Hyde Park, Delhi, Anderson, Green Township, Westwood, Mount Healthy, Finneytown, North College Hill, Northside, Springfield Township, Forest Park, New Richmond, Bridgetown, Wyoming, Madeira and Bond Hill in Ohio, and in Fort Mitchell, Taylor Mills, Fort Thomas, Latonia, Covington and Florence in Northern Kentucky, according to Mount Saint Joseph researchers.

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Brood X covers much of western Ohio and Indiana, stretching from Michigan down to Tennessee. It also covers a swath of Maryland, Pennsylvania, Deleware and New Jersey and includes smaller areas in a few other eastern states.

Most cicada broods in the U.S. emerge just once every 17 years as part of the insects’ unusual life cycle. Cicadas spend most of their lives burrowed, slowly maturing until they all emerge at once, breed and die.

The researchers at Mount Saint Joseph University are asking for help mapping the cicadas this year. For information on how to help, check out their website here.