Fact check: Brood X cicadas are infected with a sexually transmitted fungus

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The claim: Brood X cicadas are infected with a sexually transmitted fungus

After a 17-year hiatus, the cicadas are back together, once again serenading the southeast U.S. with their shrill melodies while they do what they do best: mate.

However, lurking behind the scenes of this planned orgy is something that rings less cacophonous and more nefarious.

"There's a fungal STD going around among Brood X (a reference to this year's crop of cicadas)," claims a June 8 Instagram post. "The fungus infects the cicadas and causes their rear-ends to fall off."

The post also says the fungus, called Massospora, particularly infects the brain of the male cicada, compelling it to mimic the female's body language, which encourages amorous advances from its fellow males.

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But is there any proof of this? Experts say Massospora does indeed infect the thumb-sized insect, secreting mind-altering chemicals that impact male mating behavior. But it doesn't directly infect the male cicada brain and sexual transmission is not the only way it spreads.

Fungus is sexually transmitted, but infection can happen before

Scientists have known about the fungus Massospora and how it selectively infects cicadas since the 19th century. What they didn't know, up until a few years ago, was how exactly it was able to change the insect's behavior, especially during mating.

Unlike other infectious fungi that typically kill their hosts – like the parasitic Ophiocordyceps known to infect carpenter ants – Massospora secretes mind-altering neurochemicals that act on a cicada's brain, said David Shetlar, an entomologist and professor emeritus at Ohio State University.

In an email to USA TODAY, Shetlar said an amphetamine, known as cathinone, is secreted by a type of Massospora that only infects periodical cicadas, the ones that appear every 13 to 17 years.

Amphetamines are powerful neurological stimulants that speed up functions of both the brain and the body in humans resulting in increased wakefulness, reduced fatigue and inhibition. But on the flip side, these stimulants can also cause detrimental effects like heart attack and death.

Scientists hypothesize cathinone has a similar effect in cicadas, keeping them awake, more active and, perhaps, more interested in mating, said Brian Lovett, a post-doctoral researcher studying insect-destroying fungi at West Virginia University.

Cathinone causes infected cicadas to fly more than usual and male cicadas to flick their wings like females – a gesture indicating mating interest.

Interestingly, the fungus does this without directly infecting the male cicada's brain.

"We have no evidence that the fungus is infecting the brain directly," Lovett told USA TODAY via email. "Instead, this fungus grows within (and eventually replaces) the abdomen of infected cicadas. From there, the fungus makes and secretes chemicals that manipulate the brain from afar."

And sexual contact is not the way the fungal spores are spread.

Wing flicking by both infected males and females tends to scatter spores to neighboring, non-infected cicadas, said both Lovett and Shetlar.

There are indications young cicadas, known as nymphs, may be infected even before interacting with any other cicada when they first emerge from underground.

"The early signs of infection would suggest that the nymphs may actually encounter the spores when they construct their emergence burrows and chimneys, often a month before actual emergence," Shetlar said.

Humans can rest assured though: Massospora doesn't pose any danger to health or food, Lovett said. (Although the FDA warns adventurous gourmands with shrimp allergies should steer clear of eating cicadas.) The fungus also doesn't threaten the survival of the cicadas themselves since they emerge in large numbers and Massospora doesn't infect every single one.

It's worth noting, another species of Massospora, known as Massospora levispora, infects annual cicadas which are found throughout the world (in the U.S., mostly in the West) and live for much longer than their periodical brethren. Instead of an amphetamine, this variant releases a hallucinogenic substance called psilocybin, commonly known as magic mushrooms.

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"The behavioral effects of (psilocybin) are less studied, but likely also causes abnormal behavior in the infected individuals," said Shetlar.

Our rating: True

Based on our research, we rate as TRUE the claim Brood X cicadas are infected with a sexually transmitted fungus. The fungus, known as Massospora, secretes neurochemicals that affect the cicadas' mating behavior, particularly making male cicadas flick their wings like females, thereby confusing fellow males.

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This article originally appeared on USA TODAY: Fact check: Brood X cicadas infected with sexually transmitted fungus

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