NASHVILLE, Tenn. (WKRN) — All across the southern and midwestern portions of the United States, large broods of periodical cicadas are preparing to emerge from underground.

Brood XIX, the largest periodical cicada group, is set to emerge in mid-May 2024 in over a dozen states: Alabama, Arkansas, Georgia, Illinois, Indiana, Kentucky, Louisiana, Missouri, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee and Virginia. These cicadas, which emerge every 13 years, usually stick around through mid-June.

Around the same time, another cicada brood known as Brood XIII — which emerges every 17 years — will be surfacing in northern Illinois, but also as parts of Indiana, Iowa, Michigan and Wisconsin.

As usual, these cicadas will be present in huge numbers, which researchers believe allows them to overwhelm any predators that would otherwise threaten their ability to breed.

“They overwhelm you with numbers,” Dr. Frank A. Hale, of the University of Tennessee’s Extension program, told Nexstar’s WKRN. Hale estimated that some areas may see up to a million cicadas per acre.

Their only goal, he said, is to lay “millions of eggs and keep the species going” before completing their life cycles and dying off at the end of the breeding period.

There are many species of cicadas, but they all fall into two categories: annual and periodical. Annual, as the name suggests, are present every year — and the sounds they make are generally what you might associate with the noises you’d hear on a typical summer night. They have green bodies and black eyes and are most active during the evening and nighttime hours.

Periodical cicadas have life cycles of either 13 or 17 years, emerging after underground development in large groups called broods. Instead of green bodies and black eyes, periodical cicadas have red eyes and can look especially striking immediately after molting.

When these periodical broods emerge in large numbers, they can be loud. Really loud.

“I’ve heard 100 decibels. That’s like a lawnmower or being in [Knoxville’s] Neyland Stadium during a football game,” said Dr. Hale.

The noises emanate from a structure on the males’ exoskeletons called “tymbals,” which they use in mating calls. The females will then respond by snapping their wings, signaling to the males that they are open to mating.

Hale said a male cicada can also be drawn to the sound of someone snapping their fingers, as it can’t tell the difference.

“So if you find one by itself, you can click your finger, and you can make it come to you,” Dr. Hale said.

Even if you have no interest in seeing a cicada up close, a vast number of emerging insects makes them a popular food source for various animals, including snakes. Copperheads, in particular, seek out cicadas when they are plentiful. According to Dr. Hale, some larger species also enjoy snacking on cicadas.

“I’ve heard reports of bears eating them as they come out of the ground, raking them with their claws, and just all the animals get satiated; they get filled up. They can’t eat anymore.”

Humans, too, have been known to eat cicadas, and those who have tend to say they taste like shrimp. The Food and Drug Administration, however, has warned that cicadas, which share “a family relation to shrimp and lobster,” should not be consumed by anyone allergic to shellfish.

Otherwise, cicadas are “generally harmless” to the environment, the Environmental Protection Agency says. They do not bite or carry diseases, and they won’t eat “leaves, flowers, fruits, or garden produce,” according to the EPA. Young trees, on the other hand, will need to be covered in protective mesh, as the insects can damage saplings while laying their eggs in the branches.

“Cicadas cannot harm larger, more established trees,” the EPA writes.