AUDIE CORNISH, HOST:
In a few weeks, billions of periodical cicadas will emerge from the earth and swarm the treetops of 15 states in the Midwest and East Coast. This brood of insects has been underground since 2004. Reporting from member station WAMU in Washington, D.C., Jacob Fenston tells us their behavior may be changing, and climate change is one possible culprit.
JACOB FENSTON, BYLINE: The last time the periodical cicadas emerged in Washington, John Kerry was running for president. Barack Obama was an obscure baby-faced state senator. Donald Trump was praising Democrats on CNN. Ploi Swatdisuk was a senior in high school.
PLOI SWATDISUK: I'm actually a little anxious about it. Like, they should be here now, shouldn't they? Like, when are they coming?
FENSTON: She remembers back in 2004, the large beady-eyed insects making a deafening chorus, their shiny bodies blanketing sidewalks and lawns.
SWATDISUK: It's just so gross, like just splotches of when people are trampling them. So I'm not really looking forward to it. And I don't know who could be except, like, maybe wildlife biologists.
MICHAEL RAUPP: This is our Super Bowl, absolutely. For entomologists, we've been looking forward to this.
FENSTON: Mike Raupp is a professor emeritus at the University of Maryland, also known as the Bug Guy. What Swatdisuk recalls as kind of gross and inconvenient, he calls a spectacular event. These insects have been underfoot silently sucking sap from tree roots for almost two decades.
RAUPP: Remember, these are just teenagers, and they've been underground for 17 years. It's been a dismal existence. They want to come up and party.
(SOUNDBITE OF CICADAS BUZZING)
FENSTON: There are more than a dozen different cicada broods scattered across the eastern half of the U.S., all on different 17- or 13-year schedules. But why do cicadas wait so long underground? To understand, Raupp says you have to consider cicadas' peculiar survival strategy. It's something called predator satiation.
RAUPP: In other words, they're going to emerge synchronously in such massive numbers, they fill the bellies of every predator that wants to eat them.
FENSTON: Even after predators' bellies are full, there are still many, many cicadas left to reproduce. But for this satiation strategy to work, cicadas have to all emerge the same year in overwhelming numbers. If just a few come out on an off year...
RAUPP: They are eaten into oblivion.
FENSTON: As for the 17 years underground, Raupp says emerging only in prime number intervals helps cicada broods on different schedules avoid each other. Intermixing could mess with those precisely timed schedules, dooming cicadas. But lately, cicada schedules seem to be changing. John Cooley is a professor at the University of Connecticut. Years ago, he started a project mapping cicada broods. Whenever periodical cicadas start emerging, he and his colleagues drive around with the windows down.
JOHN COOLEY: Kind of putter along a little bit slowly - you're not flying down the road at top speed.
FENSTON: They listen for cicadas and map what they hear. In recent years, they've been hearing something unexpected - cicadas emerging years early off schedule. And he says it could be because of the warming planet.
COOLEY: So it is an absolutely intriguing possibility that as global climates change, it's throwing the cicadas off the cycle.
FENSTON: Another possibility - cicadas haven't changed their behavior; humans have. Armed with smartphones and the Internet, we're reporting cicada sightings more often. Some early reports are already coming in, but the masses of cicadas aren't expected until mid-May. For those who aren't excited about that prospect, Cooley has some advice - try to appreciate it for the unusual event it is.
COOLEY: This is something that, at this scale, there really isn't anywhere else on the planet where something like this happens.
FENSTON: In the midst of what's been a terrible pandemic year for most of us humans, the emergence of the periodical cicadas is a moment to pause and marvel at nature. After all, who knows what life will be like next time this brood comes out in 2038?
For NPR News, I'm Jacob Fenston.
(SOUNDBITE OF SONG, "THE BOYS ARE BACK IN TOWN")
THIN LIZZY: (Singing) I said, the boys are back in town. Transcript provided by NPR, Copyright NPR.