After Eclipse: Nature's next big show — cicada double emergence

The sight and sound of trillions of cicadas surfacing across much of America, a massive invasion of two separate groups called broods emerging at the same time, has scientists buzzing.

For the first time in more than 200 years, two broods -- Brood XIX, known as the "Great Southern Brood," and Brood XIII, known as the "Northern Illinois Brood" -- will emerge from the ground simultaneously.

While there is not extensive overlap between the two broods, some regions, especially in America's heartland, will experience a double-whammy of cicada occupation, experts told ABC News.

Cicadas will be everywhere -- their nymphs and exoskeletons will litter the ground and adults will be seen on trees and nearby plants throughout suburban areas as well as flying around in the air, Evan Lampert, a professor in the Department of Biology at the University of North Georgia, told ABC News.

It will be an "amazing experience" to witness the insects come out of the ground to mate and lay their eggs before they disappear back into the ground, Tamra Reall, an entomologist at the University of Missouri, told ABC News.

"It's magical, and that's part of their name," she said. "Their genus name is magicicada, and it's because it's a magical experience."

Scientists like Reall believe the solar eclipse will serve to amplify the excitement surrounding this experience. She observed that both events coming so close together will give the public "a chance to see science in action, nature in action, and see them working together.”

Here's what to expect from this year's historic cicada event:

A once-in-a-lifetime cicada emergence

Some broods of cicadas emerge every year, which is why residents in regions that experience regular emergences may not immediately understand the significance of this year's event, according to entomologists.

The mass emergence that comes when these two broods dig up from beneath the ground will be a far cry from the annual occurrences, David Althoff, a professor at Syracuse University's Department of Biology, told ABC News. Residents in about a dozen states from Maryland to Oklahoma, and from Illinois to as far south as Alabama and Georgia, can expect to see cicadas from these periodical broods, according to the University of Connecticut's Periodical Cicada Information Pages.

Brood XIX, the largest geographic extent of all periodical broods, surfaces every 13 years, while Brood XIII emerges every 17 years. The last time these two broods emerged together was in 1803 -- when Thomas Jefferson was president of the U.S. -- and the next time they will co-emerge is not expected for another 221 years, until about 2245, forecasts show.

When multiple periodical broods surface at once, it's typically in different parts of the country, Keith Clay, a professor at Tulane University's Department of Ecology and Evolutionary Biology, told ABC News. An adjacent emergence of two large broods is rare.

"It's just a statistical anomaly, like Halley's Comet," Clay said.

Central Illinois will be one of the few regions that will experience the double brood emergence, entomologists predict. The greatest likelihood of contact between the two broods is near Springfield, researchers predict.

"I've been looking forward to this for many years," Catherine Dana, an entomologist at the Illinois Natural History Survey, told ABC News.

When are the cicadas expected to emerge?

By mid-April, many residents will begin to see holes appear in their yard as the nymphs come closer to the surface.

Entomologists expect cicadas to begin popping out of the ground later in the month, they told ABC News.

The slow buildup will continue into May, and people can expect to hear them once the adults begin to surface in synchronicity, Althoff said.

"Once they come, they come fast," Lampert said.

Cicadas spend the majority of their lifespan underground, where they feed on tree roots. Therefore, they will mostly congregate on or around trees when they come up, the researchers said.

A few weeks after the unmistakable noise of the male cicadas' call begins, the adults will fall to the ground and the nymphs disappear into the soil once again.

Why cicadas emerge in mass numbers

Scientists believe the cyclical emergence of the periodical cicadas is a survival mechanism for a species that has no defenses and a high mortality rate.

Surfacing only after such long gaps and doing so in such vast numbers ensures that although they are easily preyed upon by other animals, plenty will survive to spawn a new population to return underground for the next 13 or 17 years.

Animals such as birds, mice and squirrels eat the cicadas but often get "sick" of them because they eat so many during the feeding frenzy, Althoff added. Ants and wasps sometime eat them as well, Lampert said.

Entomologists estimate that the dual emergence could bring trillions of cicadas above ground by late May, at the peak of their periodical breeding time of four to six weeks.

"This is a natural wonder of the world. Like there is no other organism, at least, that I know of in North America, that has this sheer amount of biomass," Dana said.

The periodical nature of the surfacing events could also be a way to prevent hybridization among species, Althoff said.

Why cicadas are so loud

Cicada populations are an omnipresent source of sound during their time above ground.

The flying variety that emerge each summer in many areas provide a familiar buzzing symphony. The high-pitch call of the males can be described as a cross between a rattling sound and the buzzing of bees, Althoff said.

But the collective concert of these periodical cicadas, mating calls actually, rising next to one another will be a louder, haunting mix of sizzling noise, buzz-click sounds, and droning that, according to John Cooley, an entomologist at the University of Connecticut, "can be pushing 120 decibels if you're right inside that chorus." He adds, "that's sort of like getting too close to a jet engine."

The male cicada anatomy includes a specialized washboard-like structure under their forelegs called a tymbal that they strum with their legs, Clay said.

How temperatures affect cicada emergence events

The general rule of thumb entomologists use for predicting when cicadas will begin to surface is once the topsoil in a region reaches about 64 degrees Fahrenheit, Lampert said.

Therefore, the southernmost states experiencing the warmest temperatures will experience the first cicada sightings, Lampert said.

Warming global temperatures also present the opportunity for cicadas to emerge sooner in a season, but that remains to be seen, the experts said.

The volume of the cicada calls is also affected by atmospheric temperatures, Clay said. The warmer it is, the more vocal the cicadas are.

"If the temperature goes below 75 [degrees], you can immediately hear a drop in the sound level of the adult male cicadas singing," he said.

Can you eat the cicadas?

The sudden, mass emergence of cicadas offers up opportunities for sustainable sustenance, according to experts.

Like many bugs, cicadas are packed with protein, and "They feed everybody, including fish, snakes, small mammals, large mammals, birds," Dana said. "I like to think of this event as potentially buffering some of the losses that we've seen in our wildlife [populations]."

Humans can also enjoy this bug buffet. "They are indeed edible," Reall confirms.

"There's always some adventurous people who get together and have a cicada potluck," said Clay, who has seen cicadas put in soups, bread and brownies. He said they taste "like asparagus."

Menus for cicada dishes and cocktails emerge with each emergence of periodical cicadas, evident in the online cookbook devoted to cicada cuisine published by the University of Maryland in 2021 called "Cicada-licious."

During another mass emergence several years ago, Sparky's Ice Cream in Columbia, Missouri, featured cicada ice cream. Boiled and candied, the bugs were made into a cold concoction "basically like a butter pecan flavor," manager Tony Layson told ABC News.

But the shop pulled it from the menu after only 90 minutes when the state's health department nixed its sale, Layson said.

Insectivores interested in trying cicadas should be cautious about where they harvest their meal, avoiding cicadas gathered near where insecticides or other chemicals have been used. They should be properly cooked and devoured before their exoskeleton hardens, "when they are still soft and squishy," Dana said.

What humans need to know about dealing with cicadas

People who hate bugs will not be able to escape the presence of cicadas, Althoff said.

"They'll be noticeable," he said. "There's no doubt you're gonna see them."

Cicadas are not poisonous, and they do not bite or sting. Althoff reminds his students at Syracuse to remain calm when the events occur and watch where they're walking, he said.

"They really don't do anything to kind of harm humans," Althoff said. "I mean, it might be an annoyance, but people don't have to be afraid in terms of like getting bitten."

People may start to see dead branches on trees from where the cicadas fed on the sap, Lampert said.

But any harm cicadas cause to plants at the surface is temporary and outweighed by the benefits they provide, experts said.

They provide a feast for other species while on the surface. Once the multitudes die and fall to the ground, their decay releases nutrients back into the soil.

Lampert advised people to prepare themselves for the "deafening noise," especially if they have never experienced a cicada emergence before.

How to help cicada researchers

Researchers will be relying heavily on citizen science in their quest to study these periodical cicada broods.

Lampert suggested scientific organizations such as Cicada Safari and iNaturalist for people to submit photographs and sightings of the cicadas.

The event will be a good reminder to people about the kinds of insects that exist, especially since cicadas aren't always visible, Althoff said.

"Most of the time we think about them as being kind of annoying and something that we don't want to interact with and we tend to we tend to ignore them," he said. "But it's pretty fantastic to see this many insects that have been hidden in the ground that emerge all at once."