The periodical cicada emerges after 13 or 17 years underground, covering trees and towns across the eastern US
Credit : Mark_Kostich, Shutterstock
They’ve spent 13 to 17 years underground—and now they’re back in swarms. But why are Americans calling them “zombie cicadas” this time?
In a scene that feels straight out of a horror film, millions of cicadas are crawling out from beneath the soil across the eastern United States—loud, red-eyed, and ready to mate. These aren’t your average garden pests. They’re part of a bizarre natural cycle, re-emerging only once every 13 or 17 years in massive synchronised waves.
And thanks to a freak fungal infection that hijacks their bodies and turns them into hyperactive, sterile spreaders, some have earned a chilling new nickname: “zombie cicadas.”
Cicadas Emerge After 17 Years, and Some Turn into Zombies
Every 13 or 17 years, depending on the brood, periodical cicadas rise from the earth to sing, mate, and die. This spring, something extraordinary is happening: two separate broods—one on a 13-year cycle, the other on 17—are emerging at the same time. That only happens once every 221 years.
Once they surface, the cicadas spend a few frenzied weeks flying into trees, calling out to potential mates with an unmistakable screech (which, by the way, can be louder than a lawnmower). Then, just as suddenly as they arrived, they vanish again.
But here’s where things get weird. Some of these cicadas are infected by a mind-controlling fungus called Massospora cicadina. It eats away at their abdomen, makes them sterile, and changes their behaviour in eerie ways. The infected insects keep mating—or trying to—while unknowingly spreading fungal spores. They don’t even realise their bodies are falling apart. Hence the nickname: “zombie”.
Why zombie cicadas stay underground for 13 or 17 years
The reason cicadas wait more than a decade to emerge is actually brilliant: survival by numbers. When they finally rise en masse, there are so many of them that predators, birds, reptiles, rodents, simply can’t eat them all. It’s a numbers game. Outlast your enemies, flood the food chain, and enough of you will survive to lay eggs and start the next cycle.
It’s a clever evolutionary strategy that works—especially since cicadas don’t bite, sting or carry disease. They’re not dangerous, just noisy and a little inconvenient (especially when they start flying into your windscreen).
Compare that with the southern European cicadas, like the ones you’ll hear in Provence or the Costa Blanca: they emerge every summer, usually after 2 to 5 years underground, and aren’t nearly as synchronised or overwhelming.
Are Zombie cicadas dangerous? Not at All and they might help
Despite the drama, there’s no real danger. Cicadas don’t attack humans, and they’re not pests in the traditional sense. The only “damage” they do is when females lay eggs in tree branches, which can cause minor pruning. But in many cases, that “damage” ends up helping the trees by encouraging new growth.
So if you’re in the US and hear a rising chorus of shrill calls echoing through the trees, don’t panic. It’s just nature doing its weird, wonderful thing. And for once, a “zombie outbreak” is more fascinating than frightening.
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