If you think humans experience the worst sexually transmitted diseases (STDs), you’re dead wrong. A bizarre STD affecting periodical cicadas causes their host’s genitals to fall apart and makes the insects hyper-sexual, resulting in a rapid spread of the infection.

The source of this disease is Massospora cicadina, a fungal pathogen. This parasite only infects the Great Southern Brood and the Northern Illinois Brood which emerge only once every 13 and 17 years respectively. 

The year 2024 is quite special for many cicada enthusiasts and insect lovers as both broods will emerge simultaneously. The last time such a “double cicada” event occurred was in 1803 — over 220 years ago. In May, trillions of cicada nymphs will come out of the ground, and within 10 days, they will all turn into adults ready to mate. 

However, what they’re not ready for is a deadly fungal parasite.

Once M. cicadina infects a cicada, “they’re completely at the mercy of the fungus. They’re walking dead. The infection works like a sexually transmitted zombie disease, making this case even stranger than science fiction.” John Cooley, an expert on periodical cicadas and a professor of Ecology at the University of Connecticut, told the Associated Press.

The fungus turns cicada lives upside down

Scientists suggest that about five to 10 percent of periodical cicadas develop the fungal infection but when exactly M. cicadina infects the insects is still unknown. However, one can easily differentiate between a healthy and infected cicada by looking at their abdomens. The latter develops a chalk-like plug at its rear and its genitals disintegrate. 

“It looks as if the backside of the cicada is being replaced either by chalk or by like one of those nubby middle school erasers,” Matt Kasson, an expert in fungal biodiversity and an assistant professor of plant pathology at West Virginia University, told NPR.

However, this is just the beginning of the infection. The fungus takes control of one-third of the insect’s body and continues to consume it from inside. The infected cicada soon also loses its limbs, but it keeps on mating with other cicadas until its death. Since the insect has a chalky plug instead of any real genitals, the mating doesn’t result in procreation but only contributes to spreading the infection to other cicadas.

“There’s this hyper-sexualized behavior. So, males, for example, will continue to try and mate with females — unsuccessfully, because again, their back end is a fungus. But they’ll also pretend to be females to get males to come to them. And that doubles the number of cicadas that an infected individual comes in contact with,” Kasson said.

But that’s not all. “Periodical cicadas have interlocking genitalia. So, when they pull apart, guess what happens? Rip. And then there’s a cicada walking around with someone else’s genitals stuck to them,” Cooley said.

This rip-off results in the rupture of the chalky plug. So, as the infected insect flies around, fungal spores continue falling from its abdomen. Scientists refer to such cicadas as “saltshakers of death.” However, not every infected cicada ends up disemboweled after mating. In many cases, the chalky abdomen instead bursts after an infected cicada dies, releasing M. cicadina spores in the soil. 

Periodical cicada nymphs may catch the infection from these spores when they first emerge. However, there is no evidence that confirms this theory.

Can you also become hypersexual by eating an infected cicada? 

Scientists have found that the chalky plugs of infected cicadas are loaded with cathinone (a type of natural stimulant). This chemical has different effects on different types of nervous systems. So for instance, while it turns cicadas into hyper-sexual zombies, in humans, it causes high blood pressure, alertness, euphoria, and other effects similar to those seen in individuals exposed to amphetamine. 

However, consuming an infected cicada won’t trigger even these effects in humans because it carries only a tiny dose of cathinone. Still, one should avoid eating such cicadas for their safety, according to Kasson.

When it comes to animals that feed on periodical cicadas, not much is known except that birds that feed on infected cicadas may experience hallucinations. 

Hopefully, this multiple-cicada event will help scientists better understand the fungal infection and its effects on other wildlife in greater detail.