Cicadas have emerged in South Carolina — and they're so loud some people are calling 911. Here's what to know about this year's emergence.

The harmless bugs have been spotted in North Carolina and Illinois, too, as billions are expected to emerge in the U.S. this spring.

Cicadas are coming in droves to the United States. Here's what to know. (Getty Creative)
Cicadas are coming in droves to the United States. (Getty Creative)

It’s the spring of the cicada. These buzzy insects are coming out in droves, thanks to an unusual synchronized natural phenomenon. This mating ritual occurs once every 221 years, and it involves two broods of insects with homes next to one another in the United States. However, whether or not you witness the trillions of cicadas emerging from the ground — or, more accurately, hear them, since the cicadas' mating call can reach up to 100 decibels, about as loud as a subway train — depends on where in the United States you live.

South Carolina residents are now all too aware of their buzzy neighbors: the emerging cicadas are so loud, a sheriff's office in the state reported receiving multiple calls about the unexpected noise. Cicadas have also been spotted in North Carolina and Illinois.

What should you know about the latest cicada phenomenon, which also involves hypersexual “zombie” cicadas? Here’s all the information you need.

Cicadas are medium-to-large insects known for their loud buzzing sounds, which are made by males to attract mates. They have a beetle-like body, short antennae and two pairs of transparent wings. They spend most of their lives underground as nymphs, feeding on grass and tree roots, until they emerge to mate. Once above ground, they shed their nymph exoskeletons, leaving behind empty shells attached to trees or other surfaces. This process is called molting, and it allows the adult cicadas to grow and develop wings, which enables them to fly and reproduce.

When they emerge from the ground depends upon the type of cicada. There are annual cicadas, which emerge every year, as well as periodical cicadas, which emerge every 13 or 17 years in massive numbers. Now, these 13- and 17-year cycles are syncing up.

The cicadas are coming home to roost! Or, rather, mate. Thanks to the synchronization of the 13- and 17-year-cycle cicadas — which only happens once in every 221 years — trillions of periodical cicadas known as Brood XIII and Brood XIX are emerging from the ground for a mating ritual.

This noisy ritual, which begins four to five days before the cicadas emerge, peaks with the male cicadas loudly buzzing in hopes of securing a mate. The cicada song can reach up to 100 decibels. Here's how it sounds:

These two cicada groups happened to make a home next to one another but won’t overlap too much, with the exception of parts of Illinois. Brood XIX will appear in parts of the Midwest and Southeast, in states like Missouri, Illinois, Louisiana, North Carolina, South Carolina, Virginia and Maryland, while Brood XIII will primarily be seen in Illinois while also extending into parts of Wisconsin, Ohio and Iowa.

Cicadas will emerge earlier in warmer parts of the country, with the earliest-known appearance coming in mid-April. Most cicadas, however, are expected in mid-May or early June. The whole cycle lasts about a few weeks after they emerge.

The cicadas may be extra-frisky this year, thanks to a sexually-transmitted fungal pathogen called massospora cicadina that makes them very eager to mate. Unfortunately, it’s not all fun and games for the cicadas, as this fungus essentially zombifies them.

While these cicadas are not literally undead, the cicadas infected with the fungus, which has mind-controlling elements similar to that of hallucinogenic mushrooms, have their backsides taken over by chalky white fungal spores. This ultimately causes their genitals — as well as other body parts — to fall off, meaning that the fungal infection is ultimately fatal. What’s particularly strange is that these infected insects also exhibit hypersexual behavior as a function of the fungus — so when they do attempt to mate, they spread the fungus. While we don’t know how many cicadas are infected with the fungus, in 2020, 10% of a brood of cicadas in the Midwest were infected.

The good news? These cicadas, zombified or not, are harmless to humans.