This May, billions of cicadas from Brood X are set to burst forth from the soil of the eastern United States after 17 years leading mysterious lives underground. The emergence is the loudest part of a life cycle that began when adult cicadas deposited their eggs on tree branches. Nymphs hatched, fell to the ground, burrowed into the soil and fed on fluids sucked from the roots of plants and trees for years. When the temperature warms this spring, they will rise up from the dirt. Cicadas are chunky, noisy insects with bright red-eyes, so if they’re emerging in your area you can expect to be well aware of them. The raucous four to six week-long event rages until all the participants die and litter the forest floor. Experiencing the throng of insects in person is a surefire way to be amazed. But whether you can stand amongst the buzzing blizzard of bugs or not, we’ve gathered a slew of astonishing facts that will make you appreciate the insects.
Brood X will appear in 14 states
When the soil about eight inches below the surface reaches 64 degrees this spring, cicadas from Brood X will start to claw their way towards the light. They’re expected to emerge by the billions across 14 states, with the epicenter in the District of Columbia, Maryland and Virginia, reports Darryl Fears for the Washington Post.
Brood X is one of 15 broods of periodical cicadas—groups that emerge from the ground on the same time cycle—in the U.S. Twelve of those broods operate on 17-year cycles and the other three poke their heads above ground every 13 years. Researchers trying to map the geographic extent of Brood X encourage anyone enthusiastic about recording their sightings to use the Cicada Safari app. However, if you do go the citizen scientist route, be careful to differentiate the bona fide Brood X emergence from stragglers. In the world of periodical cicadas, stragglers are any individual insects that fall out of sync with their brood’s emergence schedule. Straggler emergences tend to be patchy and scattered compared to the main emergence. Brood X’s 2021 emergence is likely to have even more stragglers than usual because two other adjacent broods have emergence schedules that are four years before and after it, according to researchers at the University of Connecticut. So, if a smaller, lower density patch of cicadas crops up, especially in an area at the limits of Brood X’s range, it’s possible the bugs may not be from Brood X at all.
Brood X is a muse
Back in 1970, three cycles ago, Brood X’s buzz-saw-like calls inspired Bob Dylan to write the song “Day of the Locusts.” Dylan heard the cicadas while receiving an honorary degree from Princeton University and the insects inspired these lyrics:
As I stepped to the stage to pick up my degree
And the locusts sang off in the distance
Yeah, the locusts sang such a sweet melody
Oh, the locusts sang off in the distance
Yeah, the locusts sang and they were singing for me
The 1936 Ogden Nash poem “Locust-lovers, attention!” was also inspired by Brood X. The work was first published in the New Yorker and was later collected in Nash’s book I’m a Stranger Here Myself. Here’s a snippet:
Overhead, underfoot, they abound
And they have been seventeen years in the ground.
For seventeen years they were immune to politics and class war
and capital taunts and labor taunts,
And now they have come out like billions of insect debutantes
Cicadas are not locusts
Dylan and Nash shared the misapprehension that the periodical cicada is a type of locust. It is not.
Locusts are a type of short-horned grasshopper and belong to the order Orthoptera along with all other grasshoppers and crickets, while cicadas are Hemipterans which are considered “true bugs” and include aphids and planthoppers.
But, at least in the U.S., this taxonomic distinction has not stopped people from calling cicadas locusts. As Max Levy reported for Smithsonian last summer, early colonists saw hordes of emerging cicadas and quickly misidentified them as locusts. “They were thought of as a biblical plague,” John Cooley, an assistant professor in residence at the University of Connecticut, told Levy. Indeed, a group of cicadas is still referred to as a plague or a cloud. “The question I get the most is ‘How do I kill them?’” Cooley told Levy.
Cicadas have one of the longest insect lifespans
The 13- or 17-year lifespan of periodical cicadas is one of the longest of any insect, but only a tiny fraction of that time is spent above ground. The rest of a periodical cicada’s life is spent underground as a nymph feeding on liquid sucked from plant roots. Over their many years beneath the soil, the nymphs shed their exoskeletons, a process known as molting, five times.
Writing for National Geographic, Amy McKeever reports that the nymphs count the years by detecting the uptick in fluid flowing through the roots they feed on that occurs during each year’s spring growing season. After 13 or 17 cycles, periodical cicadas wait for the soil temperature to reach around 64 degrees before digging their way back to the surface.
Once topside, the nymphs climb up into the trees where they proceed to plant themselves on a branch and transform into winged adults by once again shedding their exoskeletons. At first, the red-eyed adults are a ghostly white with soft, curled-up wings unfit for flight, but their bodies soon harden and turn black and the now rigid wings can finally float the chunky two-inch bug into the air.
Cicadas inundate forests as a survival mechanism
By emerging all at once in densities of up to 1.5 million per acre, cicadas manage to overwhelm predators, from songbirds to skunks, who quickly get too full to take another bite of the buzzing buffet.
“It’s very much like when you go to an all-you-can-eat crab feast,” Gaye Williams, an entomologist for the Maryland Department of Agriculture, tells Darryl Fears of the Washington Post. “The very first bunch that you throw down on your table, everybody grabs crabs and you start cracking them, and you take every last molecule of crab meat. About the fourth tray … people only take the claws. As this orgy of eating goes on, there are animals that actually won’t touch them anymore. They’re full.”
Once the raccoons, frogs, snakes, squirrels, possums and any other animals interested in an easy meal can’t eat anymore, the cicadas are free to go about their business of spawning the next generation.
Humans eat them, too
Animals aren’t the only ones that chow down on the cicada buffet. Humans also get in on the act. Claims about what they taste like vary, with some people comparing them to shrimp, others to asparagus and a few people even mentioning peanut butter. But before you go wild eating cicadas, please note that they may contain elevated levels of mercury and can cause allergic reactions, especially among those with shellfish allergies.
For Native Americans, the history of eating cicadas goes deep. A mid-20th century account tells of the Cherokee in North Carolina digging up cicada nymphs and frying them in pig fat or pickling them for later, reported Mark Hay for Atlas Obscura in 2018.
Near Syracuse in upstate New York, members of the Onondaga Nation eat cicadas during mass emergences like the one Brood X is about to put on, Rick Rojas reported for the New York Times in 2018. The practice ties the Onondaga people to their ancestors, who ate the bugs to survive when settlers and missionaries had burnt their crops and ransacked their villages.
Their lengthy life cycles may help them evade predators
One hypothesis for the reason behind the periodical cicadas’ seemingly inscrutable selections of 13- and 17-year increments for their reproductive cycle centers around the fact that both numbers are prime. The idea is that by popping out of the ground only in prime numbered intervals, periodical cicadas avoid ever synching up with booming populations of predators, which tend to rise and fall on two to ten year cycles, wrote Patrick Di Justo for the New Yorker in 2013.
Mathematically speaking, the logic checks out, but the thousands of cicada species around the world that don’t have synchronized brood emergences in prime increments cause cicada researchers to wonder if this is the whole story. If the periodical cicada’s unique life cycle is so uniquely advantageous, why haven’t the rest evolved similar reproductive strategies?
More than 3,000 species exist
Not all cicadas emerge every 17 or 13 years. Nearly 3,400 species of cicada exist worldwide and the majority of them conduct their emergences every two to five years. Periodical cicadas, made up of seven species in the Magicicada genus, are the only ones that spend either 13 or 17 years underground and they are only found in the U.S. Three of the Magicicada species are 17-year cicadas, while the remaining four operate on 13 year cycles. With multiple species on both schedules, periodical cicada broods often contain multiple species. This might seem strange but the predator-bombarding benefits of emerging en masse remain the same as long as the multi-species broods remain synchronized.
They can buzz louder than a lawnmower
A full-scale cicada emergence like the one coming for the eastern U.S. can reach a deafening crescendo as millions of males all call for mates at the same time. The amorous din can reach roughly 100 decibels, which is just shy of standing three feet from a chainsaw. To make their love buzz, the male cicadas rapidly vibrate a pair of white, ribbed membranes called tymbals that sit on either side of their abdomens.
Scientists from the Navy's Undersea Warfare Center have studied cicadas in hopes of figuring out how male cicadas manage to produce their incredibly noisy mating calls without expending much effort. The idea is that a device that mimicked a cicada’s method of sound production could be used for remote sensing underwater or ship-to-ship communications.
Their wings repel water and bacteria
Noise making isn’t the only arena where cicadas are providing inspiration for human inventions. The wings of some cicadas are naturally antibiotic, according to research published in 2013. The cicada’s wings kill bacteria on contact with a layer of incredibly tiny spikes and a chemical coating. The special defense doesn’t work on all bacteria, just those whose cell walls are soft enough to slump between the spikes, which stretches the bacterial cell membranes until they tear and rupture. Scientists are interested in the mechanism since it’s a way to passively destroy unwanted microbes without resorting to chemical antibiotics, the overuse of which breeds antibiotic resistant bacteria.
The same coating of nano-scale spikes or pillars that cicadas use to keep their wings free of bacteria also keeps them dry by repelling water. These super-small structures are hard to replicate but last year a team of researchers managed to make copies of the cicada wing’s complex surface using nail polish and a technique called nanoimprinting lithography. The advance might one day find a home in a new generation of rain jackets.
They can host an insect-killing fungus
Some cicadas in Japan appear to have reached a rather cozy arrangement with dangerous fungi. The fungi in question are in the Ophiocordyceps genus and are close relatives of a species that turns ants into actual zombies before bursting mushrooms right out of the insects’ heads.
But the Japanese cicadas keep small pockets of Ophiocordyceps inside their bodies to help them turn a diet of sugary plant juice into something nutritious enough to keep them alive, Ed Yong reported for the Atlantic.
However, not all cicadas rejoice when Ophiocordyceps comes calling. Several species of the parasitic fungi specialize in invading the bodies of cicadas less collaboratively. In these cases, the fungi infect cicadas while they’re underground and then cause them to dig their way back up to the forest floor before killing them and exploding mushrooms out of the corpses.
Another fungus turns the insects into zombies
Annual and periodical cicadas in the U.S. have a terrifying parasitic fungus of their own. Like Ophiocordyceps, the fungus Massospora cicadina infects cicadas while they’re rooting around in the soil as nymphs. Once an infected cicada has emerged back into the sunlight to mate, the fungus starts eating the insect’s internal organs.
As the fungus grows it castrates the cicada and replaces its butt with a white plug made of spores. Massospora also drugs the cicada with an amphetamine called cathinone and psilocybin (the psychedelic ingredient in magic mushrooms), reported JoAnna Klein for the New York Times in 2019. The precise action of the drug cocktail is still unknown but these spore-toting, hollowed out cicadas buzz on apparently unaware of what has befallen them and are especially eager to do one thing and one thing only: attempt to mate. As these horny, fungi-mutilated bugs fly around meeting members of the opposite sex they spread the deadly spores to their brethren as well as any patches of soil they fly over. “We call them flying saltshakers of death,” Matt Kasson, a fungi researcher at West Virginia University, told the Atlantic’s Ed Yong in 2018.
They have an arch nemesis that eats them alive
In the summertime, solitary, up to two-inch-long wasps called cicada killers are as single-minded as their name suggests. After mating, females take to the skies to do nothing but hunt bumbling cicadas.
When a female cicada killer grapples with her quarry in mid-air, she uses a honking, needle-sharp stinger to pierce the cicada’s hard exoskeleton and inject a venom that paralyzes the victim. The wasp then has the task of getting the considerably larger, heavier cicada back to her burrow, which can be up to 70 inches long. After dragging her immobilized prey into a special chamber she’s hollowed out along her burrow, the female wasp lays a single egg on the cicada and seals the chamber’s entrance. In two or three days, the larval wasp will hatch and begin eating the paralyzed cicada alive over the course of a week or two. For eggs destined to produce another female cicada killer, the body count is even higher: mother wasps will provision them with two or three paralyzed cicadas. The larvae are said to hold off on chewing through the cicada’s nervous system until the bitter end to keep their meal alive as long as possible.
Climate change may be scrambling their schedules
Some of Brood X’s number decided to pop out a whopping four years early in 2017 and some researchers wonder if the warmer temperatures and longer growing seasons caused by climate change could be behind the increasing number of stragglers. In 2020, Brood XIX also emerged ahead of schedule, joining a growing list of broods with significant straggler contingents.
“We’ve predicted that the warmer it is, the more we’re going to see these four-year accelerations,” Christine Simon, an entomologist with the University of Connecticut, told Levy of Smithsonian. If enough stragglers successfully reproduce, they could start a new brood on a 13-year cycle, or there could be other consequences that we can’t predict. “They’re sitting down there integrating 17 years’ worth of data on what the forest is doing,” John Cooley, an ecologist at the University of Connecticut, told Smithsonian. “And if the forest is screwed up or broken, that’s going to show up.”