A fungus could turn some cicadas into sex-crazed 'salt shakers of death'

Yellow-white fungus grows inside the cicadas, filling their insides and pushing out against their abdomens. One by one, the rings that compose the back halves of their bodies slough off and fall to the ground. Driven by a chemical compound in the fungus - and now lacking butts and genitals - the bugs try to mate like crazy.

Some researchers call these infected cicadas "flying salt shakers of death." And they're lurking among Brood X.

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Unlike other fungal pathogens, the fungus Massospora doesn't kill the insects on which it grows. Instead, it forces the cicadas to act in ways that promote the fungus's spread.

"That's what people can immediately recognize as, 'This is a zombie, this is no longer a normal cicada, something strange is happening here,' " said Brian Lovett, a postdoctoral researcher at West Virginia University who co-wrote a 2020 study about the fungus.

Scientists have known about Massospora's effects on cicadas since the mid-19th century, but the fungus has cycled back into the public eye with the emergence of Brood X. As billions of cicadas that have hidden underground since 2004 pop up through the soil, Lovett said he expects less than 10% to be infected.

Periodical cicadas, or those that appear on a fixed schedule, first encounter the fungus when they're just underground. As the insects climb from tree roots to the soil's surface and await a specific temperature, the fungus germinates and infects the cicadas, Lovett said.

About a week after the bugs emerge, signs of the fungus start to appear. The spores force the back half of the insects' bodies to fall off, Lovett said, revealing an eraser-like mass of fungus. As the cicadas continue to walk and fly, apparently oblivious to the situation, the spores fall off and infect other insects - just what the fungus is trying to provoke.

Then the cicadas spring into action as cathinone, a behavior-altering amphetamine in the fungus, takes over their brains and encourages them to ignore the fact that half their bodies are missing. That's when their sex drives rev up, and they desperately try to mate. Since their genitals are gone, their attempts at sex only serve to spread the Massospora, Lovett said.

"Now the cicada is not acting in the interest of the cicada," he said, "but in the interest of the fungus."

While infected female cicadas maintain their usual mating behavior, Lovett said the fungus makes males imitate females to attract more uninfected partners. Male cicadas usually mate by calling to females. The males co-opted by the fungus also flick their wings like females to dupe other males into attempting sex.

The result: Uninfected cicadas come into contact with the fungus, which then takes control of them, too.

In this second generation of infected insects, spores grow in thicker and heavier to survive for a long time underground once the insects die, Lovett said.

This stage of life is where the nickname "flying salt shakers of death" becomes particularly apt, he said. As the cicadas' wings beat, they propel into the air spores that look like salt as they rain down. The fungus cuts off affected insects' ability to reproduce, causing a sort of "death."

Seventeen years later, the heavy spores that fell to the ground will infect a new generation of cicadas.

"So this fungus is not only coordinating all this manipulation," Lovett said, "but it's also keeping track of two different stages."

Massospora doesn't appear to be dangerous to cicadas as a population. Although it wreaks havoc on the insects it infects, Lovett said it doesn't make them die any younger and the broods still can sustain themselves over generations.

The current generation of periodical cicadas, Brood X, offers new fodder for scientists to study this unusual fungus. Scientists still have a lot of questions about it, Lovett said, because studying it requires access to its insect hosts. He said his university's team of researchers plans to collect samples of Massospora-infected Brood X cicadas from Northern Virginia this year to study the fungus's genome.

Cicadas aren't the only insects whose behavior can be steered by mind-altering fungi. Massospora is part of an order of fungi called entomophthora, Latin for "insect destroyer," Lovett said. One fungus burns holes in flies' bodies so spores will parachute down to infect flies below, while another fungus forces insects to go to a high place when they're ready to die so that spores will rain from the air.

For most insects, Lovett noted that too little is known about their behavior to even know whether a fungus might be manipulating them.

Despite the amphetamine's ability to control cicadas, no one should expect to feel a high from eating a fungus-infected insect. The bugs have very little Massospora in them when they're in their nymph stage, one of the times when they're ideal for eating, Lovett said. Intentionally eating older, infected cicadas would still probably not impact humans.

"The amount of these behavior-modifying chemicals are enough to affect a cicada," Lovett said. "But if you were to eat them, it would be such a tiny dose that you wouldn't be able to feel anything."

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