'Bourbon brood' cicadas start emerging in Kentucky after 17-year slumber

Kentucky is known as the land of horses, bourbon and bluegrass — and soon, it will be home to a whole lot of cicadas.

Billions of the winged insects are set to emerge from underground starting this month for a weekslong, frenzied and famously noisy mating ritual.

This year, cicadas are expected to pop out of the ground in nearly a dozen states, but the emergence will mostly be centered in Kentucky and Tennessee. The insects will also appear in Illinois, Indiana, Virginia, West Virginia, North Carolina, Georgia and small portions of Pennsylvania, Massachusetts and New York.

Some have nicknamed this season’s cicadas the “bourbon brood,” because of their concentration across Kentucky.

“We’re kind of the epicenter, so it just felt like we could make it Kentucky proud,” said Jonathan Larson, an assistant extension professor in entomology at the University of Kentucky.

The bugs are known as periodical cicadas, because they spend a fixed number of years underground before coming to the surface to search for a mate. Seven broods of periodical cicadas can be found in North America, and depending on their type, they emerge either once every 13 years or once every 17 years.

This year’s cicadas belong to Brood XIV, which live on a 17-year cycle.

Larson said the “bourbon brood” moniker is apt because the insects’ periodical nature is somewhat akin to the process of distilling Kentucky’s famous whiskey.

“You have to age bourbon,” Larson said. “We put it in barrels in the dark for a long time, so it’s kind of similar.”

Cicada sightings have already begun in some southern counties in Kentucky, according to Larson, but the real show will begin in the coming weeks as the soil warms.

“I would expect in the next two weeks, we’ll really hit full stride,” he said.

When that happens, some areas will be literally blanketed with cicadas. But it's not just the sheer number of them that make periodical cicada emergences a distinct experience, it's also the ear-piercing noise that comes with it.

Cicadas emit a high-pitched buzzing that can reach up to 100 decibels. The raucous noise is actually their mating song, used to find and attract females. After the insects emerge from underground, the females have only a few weeks to find a mate and lay their eggs before they die.

“The whole thing is wild and beautiful and weird and kind of wonderful,” Larson said.

Cicadas are harmless to humans, but some people find them a nuisance, especially after the insects die and huge numbers of carcasses cover the ground.

“At this early stage, there won’t be any smells or anything, but later, in about five weeks, as many of them have died, there can be kind of a rotten, decomposing smell in some areas, if there’s big enough piles of them,” Larson said.

Thousands of species of cicadas can be found around the world, but periodical cicadas are different because they spend the majority of their lives below ground, where they feed on tree roots and wait either 13 years or 17 years before tunneling to the surface.

The first cicadas typically emerge in waves sometime in early or mid-May, but most will make their way to the surface in June when conditions are warmer. Larson said cicadas usually wait for soil temperatures to hit around 64 degrees Fahrenheit before they make their push for the surface.

The insects’ dependence on environmental cues has raised concerns about how climate change may be affecting cicadas and their mating ritual.

“If it’s warmer earlier in the year, there is the potential that they could start moving closer to the surface before they ought to,” Larson said, and this could prove deadly to cicadas, since “we could have a late freeze or extreme weather events like flooding, which we’ve seen a lot of in Kentucky.”

It’s an active area of research for scientists, who are particularly interested in studying the long-term impacts of climate change on cicada broods.

Meanwhile, in the coming weeks Larson and other bug enthusiasts across multiple states will have the chance to witness a fascinating phenomenon.

“I hope people will go and try to experience it,” Larson said. “It only happens here in the U.S. There aren’t other places that can experience this, so I encourage people to do cicada tourism if they can.”

Citizen scientists can even help with research efforts by snapping pictures of the insects and recording geographical details about sightings on an app called Cicada Safari.

This article was originally published on NBCNews.com