With their bulging red eyes and alien-like mating sounds, periodical cicadas may seem scary and weird, but some of them are speed-freak, sex-crazed zombies that have been hijacked by super-sized fungi.

West Virginia University mycology professor Matt Casson, his 9-year-old son Oliver, and graduate student Angie Macias have been tracking a pesky fungus called Massospora cicadina, the only fungus on Earth that can hijack an animal’s body to make amphetamines (a drug known as speed)—and sure enough, it’s taking over cicadas, increasing their sex drive and spreading a parasite that’s transmitted sexually.

“They’re zombies, totally at the mercy of the fungus,” says John Cooley, a cicada researcher at the University of Connecticut.

The fungus has the largest genome of any known fungus—about 1.5 billion base pairs, Casson says, making it about 30 times longer than any common fungus we know—and while the periodical cicada lives underground for 17 years (13 years in the southern U.S.), its spores typically remain underground as well.

“It’s been a mycological oddity for a long time,” says Casson, “and it has the largest genome, produces wild compounds, keeps its host active, and has a whole host of other strange characteristics.”

This year, Casson decided to ask people to send him infected cicadas from around the country, and despite his injured leg, he, his son, and Mathias traveled from West Virginia to the Morton Arboretum outside Chicago, where they reported a fungus that takes over the lower half of the cicada’s body, discarding its reproductive organs and replacing them with a rather conspicuous mass that’s white, sticky but flaky. The spores then spill out like salt from a shaker.

Infected cicadas can be hard to spot.

Ten seconds after jumping off the golf cart, Macias was in the trees, looking around. She triumphantly raised the semi in the air and shouted, “I got it!”

“That was just luck,” Oliver complained.”

“Luck, eh? Good luck,” Macias replies.

Ten seconds later, Oliver spotted another bird in the bushes next to him, and a little later the photographer spotted a third.

Kasson and his small team collected 36 infected cicadas during a quick trip around Chicago, and another 200 or so have been sent in from elsewhere. He’s still waiting for the results of an RNA analysis of the fungus.

Some cicada experts estimate that one in every 1,000 periodical cicadas is infected with the fungus, but that’s just a guess, says Gene Kritsky, a biologist at Mount St. Joseph University who has written a book about the fungus. This year’s unique double appearanceHe said the numbers could be skewed because healthy cicadas tend to stay higher in trees.

“This year’s fungal situation is business as usual and not particularly unusual,” Cooley said in an email.

Scientists debate whether the fungus burrows deep underground and then infects the cicadas that emerge after 13 or 17 years, or whether it infects newly hatched larvae as they make their way underground for more than a decade.

The fungus isn’t a parasite that kills its host, but rather needs to keep it alive, Casson said. Infected cicadas will try to mate with other cicadas, spreading the spores to their mates/victims. Males may also become hypersexual and pose as females to lure and infect other males, Casson said.

A related species of the fungus that infects annual cicadas in the West also produces psychoactive compounds in the cicadas that are more similar to hallucinogens like magic mushrooms, Kasson said. That’s why some people, even experts, confuse the amphetamines produced by infected 17- and 13-year cicadas with the highly hallucinogenic compounds in the annual insects, he said.

Either way, don’t try this at home. The cicada itself is edible, Not many people are infected.

Out of scientific curiosity, Casson experimented on one during this emergence, ensuring that it was taken from the body of a female, which was more sterile.

“It was really bitter,” Cason said, explaining that she quickly rinsed her mouth. “It tasted like poison.”