Last week, the Newberry County Sheriff’s Office was swarmed by phone calls from local residents who were concerned about a particular sound they were hearing outdoors.

“We had several calls about a noise in the air that sounds like a siren, or a whine, or a roar,” the sheriff’s office said in a Facebook post.

So, what exactly was all the buzz about?

“The sound is cicadas,” the post said. “Cicadas are a super family of insects that appear each spring. The nymphs have lived underground for 13-17 years and now this time they are hatching.”

Brood XIX cicadas may be on the rise in the Upstate, but the sheriff’s office has assured residents that the insects are just a nuisance ― not a threat.

“Although to some the noise is annoying, they pose no danger to humans or pets. Unfortunately it is the sounds of nature.” the post said.

What are cicadas, and what do they look like?

According to Clemson University, cicadas are thick-bodied, plant-feeding insects that can be found clinging to trees and vegetation. They measure 1-2 inches long and have compound eyes in shades of black and red, although some may emerge with blue or white eyes. Having two eyes is better than one, but cicadas are lucky enough to have three called the ocelli, which are located in the middle of their head. The wings of the insects are thick with prominent veins, and their antennae are small.

Cicadas are known for their loud, shrill noise and exoskeletons (discarded shells). Along with hemipterans like leafhoppers and spittlebugs, cicadas belong to the suborder Auchenorrhyncha. Their presence can be found worldwide. In the U.S., they live in the eastern and southern parts of the country.

Annual cicadas and periodical cicadas are oftentimes confused with one another. In South Carolina, annual cicadas, which are black and green, can be heard every year during the summer. Periodical cicadas are smaller at 1.5 inches. They are black with red eyes and orange veins within their wings, only emerging every 13-17 years. Broods XIX are periodical cicadas.

“People hear the annual cicadas every year,” said Eric Benson, Clemson University’s extension entomologist. “In the summertime when it’s hot, dog day cicadas can be heard. In the late afternoon or evening, you’ll hear that whining in the trees. Those are the cicadas, the males calling to the females. But you know, that may be tens of hundreds (of cicadas), not tens of thousands or millions. It’s just the sheer number that makes them so loud.”

How do cicadas produce their sound?

There are over 3,000 cicada species, each one having a distinct sound, according to Britannica. Males are the only cicadas to produce the sound, which is used to establish authority and attract females into mating. Prior to copulation, a courting call is also produced. Another use of sound is to deter predators. Periodical cicadas are louder than annual cicadas due to their large numbers.

The tymbal organ is a part of the cicada anatomy that is distinct from other insects, each male possessing a pair of the circular, ridged members on the back and side surface of the first abdominal segment, according to Britannica. When the tymbal muscle attached to the membrane is contracted, it bends, making a clicking sound. As the muscle relaxes, the tymbal goes back into place. The contractions are rapid in succession, moving 120-480 times a second and creating a sound that seems continuous to the human ear. The sound is amplified by air sacs containing resonant frequencies similar to the tymbal vibration frequencies. This is why cicadas sound like they are buzzing.

Are cicadas harmful to humans or pets?

Cicadas are not harmful to humans or pets and do not sting or bite, according to the United States Environmental Protection Agency. Although they are not a threat to pets, cats or dogs that consume too many of the tiny creatures may come down with a temporary upset stomach, which may lead to vomiting.

But if you see a cicada, don’t squash it ― these buzzing bugs have environmental benefits:

∎ They are a food source for birds and other predators.

∎ They can aerate lawns and improve water filtration into the ground.

∎ When they decompose, they add nutrients to the soil.

When will the cicadas die off?

Once male and female cicadas have mated and the female has laid its eggs, USA TODAY reports the insects will die after spending only five weeks above ground, according to National Geographic. In other cases, adult periodical cicadas live for just three or four weeks, according to Smithsonian Museum of Natural History.

Nina Tran covers trending topics. Reach her via email at ntran@gannett.com