Cicadas are returning by the trillions in the U.S. this year – a synchronized emergence that begins when the dirt reaches a precise 64 degrees. The buzzing bugs have already come out in some places – here's where.

Where will cicadas emerge in 2024?

Two cicada broods are emerging at the same time this year, meaning the U.S. will see more cicadas than usual. 

Brood XIX, which comes out every 13 years, will emerge in the Southeast in Kentucky, Missouri, Arkansas, Tennessee, Mississippi, Alabama, Georgia, South Carolina, North Carolina and Virginia.

Brood XIII, which comes out every 17 years, will be seen in the midwest, primarily Illinois and Iowa.

Cicadas live underground for most of their lives, and at the end of their 13 or 17-year cycles, they emerge, fly into the trees, molt, mate and then die. Their babies then fall onto the ground and burry themselves into the dirt while they await their next emergence.

They only come out at the end of their cycle, when the dirt reaches 64 degrees. This is expected to happen in May or June in most places, according to Ken Johnson, a horticulture educator at the University of Illinois. But some states warm up faster than others – and they've already seen cicadas emerging. 

Videos show where cicadas have already emerged

Near the Georgia-South Carolina border on April 25, CBS News National Correspondent Dave Malkoff found thousands of cicadas filling the air with their signature, loud buzzing sound. Some were seen molting, or shedding their skin, on a tree trunk.

"They take a while to turn into their full adult bodies," Malkoff said, holding a cicada. "They have to dry out and then they get their wings."

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A small section of Illinois will see both Brood XIX and Brood XIII converge this year. In Champaign, Illinois last week, CBS Chicago's Maddie Weirus went on the hunt for nymphs – or baby cicadas – with University of Illinois entomologist Katie Dana. They dug in the dirt and were able to collect samples of small cicadas. 

In some of the southern states expected to get cicadas, people have reported their emergence.

Marie Gruss Sherr captured several videos of cicadas in Durham, North Carolina. Most of them were sitting in plants.

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Cicadas are often confused with locusts, which eat plants. Cicadas instead get their nutrients from small branches. Most trees, however, will remain unharmed. 

In Georgia near Lake Oconee, one cicada spotter captured the droning noise the bugs emit when they emerge. 

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Male cicadas let out a loud humming sound to attract female cicadas, who will in turn flick their wings to signal they are available to mate.

Last week, the cicadas were so loud that confused residents in Newberry County, South Carolina actually called the sheriff's department to ask why they heard a "noise in the air that sounds like a siren, or a whine, or a roar." The department assured residents it was just male cicadas trying to mate.

How long do cicadas live?

After they've emerged from their 13 or 17-year slumber underground, cicadas have a relatively short lifespan. About five days after they emerge, they start to mate, with the females laying their eggs in woody plants, using their ovipositor, or egg-laying organ. They inject about 10-20 eggs into branches and can around 500 to 600 eggs in a season, according to Johnson.

The eggs hatch about six weeks after they're laid, but their parents die shortly after the mating process, lasting only about a month above ground. 

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Caitlin O'Kane

Caitlin O'Kane is a New York City journalist who works on the CBS News social media team as a senior manager of content and production. She writes about a variety of topics and produces "The Uplift," CBS News' streaming show that focuses on good news.