For more than 99% of their lives, periodical cicadas hardly make a sound.
Surviving underground on sap and other nutrients from tree roots, they spend a full 13 years unseen and unheard.
But when they come out, they come out by the billions, all at once. And they will be very loud.
“You will not be able to miss the sound,” said Tamra Reall, an entomologist known as “Dr. Bug” in her column for kids.
There hasn’t been a cicada emergence in Missouri as big as the one coming this spring since 2011 — and there hasn’t been one on this scale in the world since 1803.
Every 13 years, Brood XIX emerges from the soil across nearly all of Missouri in late April or May, as well as much of the southern half of Illinois and scattered parts of several states farther south.
This year in particular is unusual, though. A second major brood of cicadas will make its long-awaited reappearance this spring as well — Brood XIII, which emerges every 17 years and will invade Illinois and some surrounding states.
These two broods haven’t coincided in 221 years and won’t again for another 221.
Missouri’s last major cicada wave hit Columbia full-force in 2011. Reall, who is also a horticulture specialist for MU Extension, was here to witness it all.
“All of a sudden, in a couple-week period, there was a ton of these black cicadas that emerged with red eyes,” she said. “Trees would be covered in them.”
Reall was a graduate student in entomology at the University of Missouri in 2011, and she expects this year’s invasion to be very similar. Steve Buback, a natural history biologist at the Missouri Department of Conservation, agrees.
“They were loud. They were everywhere,” Buback said. “And it’s going to be the same way again.”
That year, Sparky’s Homemade Ice Cream concocted a cicada-flavored ice cream. County health codes ended the experiment, but it was wildly popular while it lasted.
A sign that year announced that the flavor would return in 2024, but Sparky’s manager Tony Layson said they have no plans to revive it. The promise was intended to be a joke.
“We couldn’t do it in 2011, so I don’t think we had any intention of doing it again in 2024,” Layson said.
From chorus to carcass
Periodical broods are different from annual cicadas, which are larger and don’t have the distinctive red eyes or the orange tips on their wings. Periodical cicadas are smaller, noisier and emerge earlier than the annual cicadas.
Every 13 or 17 years, periodical cicadas show up with just one goal: to breed.
“As adults, they don’t do a lot besides sing, mate, lay eggs and die,” said Buback.
They molt as soon as they leave the soil, leaving their exoskeleton husks on trees and fences, where the shells may remain for several weeks.
Emergence holes are left behind after cicadas have climbed to the surface. One trigger for emergence is when the soil temperature — as measured 8 inches below the surface — reaches 64 degrees Fahrenheit.
They typically climb into trees, where the mate-seeking males begin to sing, filling the spring and early summer air with their pulsing hum.
Male cicadas produce their mating call by pushing air through an organ on their abdomen called a tymbal, which Buback compared to a drum head. Brood XIX includes four different cicada species, each with its own slightly different song.
Cicadas spend their brief adulthood in a reproductive frenzy. Once their mating calls have been answered, females lay their eggs in a thin line on the tips of branches.
Then, after four to six weeks of life above ground, the cicadas die, gradually returning to the soil they once called home.
A cicada molt, the cicada's exoskeleton, is left behind after a cicada's wings have developed. The strong, spine-edged forelegs helped the nymph to dig through the soil, then they enable the animal to claw its way to the surface.
The branches where they lay their eggs eventually die and fall to the ground. Once the eggs hatch, the nymphs burrow into the soil, usually no deeper than 2 feet, beginning their 13 or 17 years below the surface.
Timing is everything
Scientists remain unsure how cicadas know exactly when the right number of years have passed to emerge. The predominant theory is that they sense seasonal changes in the chemicals of tree root liquids.
Once they’ve sensed the changes the correct number of times, their biological clock alerts them to tunnel out when the soil is warm enough.
Cicadas surface once the soil temperature reaches 64 degrees Fahrenheit at a depth of 8 inches in the soil, according to the Conservation Department.
Soil warms and cools more slowly than air, and based on the weather of previous years, we can be pretty assured that it will happen consistently around late April or May, Buback said. But if, for example, the area is hit with a three-week cold stretch, it could push the emergence back a week or two.
When the swarms of cicadas appear, they provide an easily available food source for an array of animals.
“It is a bonanza of food for anything that wants to eat cicadas,” said Buback. “So any birds — crows, blue jays, most of our songbirds will gorge themselves on these protein pellets.”
From pets like cats and dogs to coyotes, raccoons and opossums — pretty much anything that eats insects will have a full belly for a while, Buback said.
Taking precautions
As with any kind of insect or pest, not everyone is going to relish the idea of a bug invasion that lasts four to six weeks. It can be a lot to manage for anyone who is uncomfortable around insects, Reall said.
And yet, based on the emergence 13 years ago, the assault is not likely to be as overwhelming as it sounds.
“There were a lot, and you’d see them on the ground, but it wasn’t like the stories you hear in the olden days or when there’s been two broods that emerge at the same time in the same area,” Reall said.
Central Illinois is expected to encounter Brood XIX and Brood XIII at the same time, which may lead to especially hefty dead cicada pile-ups. Columbia will not face that problem to the same extent. Once they die, they can be swept up and tossed into the compost pile.
“They’ll be a minor nuisance for a while,” Buback said. “It’s not like we’ll have 3-foot piles.”
Cicadas don’t bite, so they don’t pose a threat of disease, but they can damage young trees. To lay their eggs, a female sticks her ovipositor — a saw-like organ on her abdomen — into the tips of finger-sized twigs, cutting a line of slits for her eggs.
Big, established trees are not going to be negatively impacted, Reall said, but the slits can damage smaller or younger trees and lead to “flagging.” Leaves on affected branches will turn brown, and the branches can break during a gust of wind.
To protect the branches, it’s important to cover young trees with mesh or cheesecloth, Reall said. Wait until next year to plant fruit trees, she said.
The cicada cycle has been around for thousands of years. Without fail, every 13 or 17 years, the insects pop up, lay eggs and die, regardless of what is going on in our human lives. Then it happens all over again.
“It’s kind of a reminder of the natural world,” Buback said. “It’s a reminder that life still persists. So kind of take note, appreciate it and know that you won’t have to deal with it again for a few years.”
