As billions of Brood X cicadas emerge, how long do they live? And what do they eat?

Cicadas are emerging after 17 years — so you may want to grab your earplugs.

Billions — or perhaps trillions — of the noisy critters are expected to descend upon 15 eastern states in the upcoming weeks, the Associated Press reported.

The insects are part of the Brood X cicadas, a group that periodically comes up from the soil to lay eggs and mate. But they won’t be here to stay.

So, what do we know about cicadas’ lifespans and diets? Here’s what experts say:

How long do cicadas live?

Brood X cicadas live below ground for more than a decade before soil temperatures signal it’s time for them to come up.

And the insects are hoping to find a spark, according to experts.

“It’s the males that are making the loud calls,” Clyde Sorenson, an alumni distinguished undergraduate professor of entomology at N.C. State University, said in a phone interview with McClatchy News. “It’s all about attracting mates and making sure that there’s another generation of these guys in 17 years.”

While above ground, female cicadas lay hundreds of eggs, which hatch up to 10 weeks later. Those cicada nymphs burrow themselves in the soil, starting the years-long cycle all over again, according to National Geographic.

Meanwhile, adults die within about a month of coming above ground, experts said.

The process has already started in some of the areas where Brood X cicadas are expected to emerge. In the next few days to weeks, the insects are set to bring their signature songs to a swath of the United States that stretches “from Indiana to Georgia to New York,” the AP reported.

What do cicadas eat?

Cicadas may harm small plants — but it’s not because they’re munching on leaves.

”Cicadas don’t eat vegetation but rather drink the sap from tree roots, twigs, and branches,” National Geographic said on its website. “Large swarms can overwhelm and damage young trees by feeding and laying eggs in them, but older trees usually escape without serious damage as cicadas don’t stick around for long.”

Usually, adult cicadas flock to ash, maple, oak and willow trees, according to pest control company Orkin. To protect smaller trees, the U.S. Department of Agriculture recommends covering them with quarter-inch netting to keep female cicadas away.

While above ground, cicadas may also become dinner for a variety of animals, including squirrels, deer, birds and reptiles. Scientists say the insects can be targets for predators because they’re readily available and easy to catch.

Some experts think cicadas emerge in such large numbers so there are enough left to reproduce after larger animals feed on some of them, according to the Penn State Extension.

“They’re actually fairly nutritious,” Sorenson told McClatchy News last week. “There’s a good amount of protein in the muscles that they have and then a fair amount of fat in their reproductive tracts.”

And yes, even humans can sink their teeth into the insects.

Online, there are recipes for everything from bug-inspired cocktails to fried cicada snacks, The News & Observer reported.

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