Spring's Bizarre Phenomenon: When Cicadas Turn into Sex-Crazed Zombies

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This spring, billions of cicadas will emerge after more than a decade underground. They will climb into the trees and sing loudly to attract mates. However, some of these insects will not be successful in their goal of reproducing. Instead, they will be controlled like zombies by a strange fungus that hijacks their bodies and behavior.

The details of how the fungus attacks the bugs may sound like something out of a horror movie. It destroys the insects' genitals, fills their abdomens with fungal spores, and makes them act hypersexually to spread the fungus. Some scientists even call the infected cicadas "saltshakers of death." According to Dr. John Cooley from the University of Connecticut, Hartford, the truth about the fungus Massospora cicadina is even stranger than fiction.

Image taken from the Extinct & Endangerd exhibition by Levon Biss, in collaboration with the American Museum of Natural History. The project shines a light upon insect decline and biodiversity, displaying insects that are either already extinct or under severe threat. The photographs by Levon Biss are created from up to 10,000 individual images using microscope lenses and contain microscopic levels of detail to provide the audience with a unique visual experience.

Image taken from the Extinct & Endangered exhibition by Levon Biss, in collaboration with the American Museum of Natural History. The project highlights the decline of insects and biodiversity, showcasing those that are extinct or facing serious threats. Levon Biss's photographs are made from thousands of individual images taken with microscope lenses, capturing intricate details for a one-of-a-kind visual experience.

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Periodical cicadas lay their eggs in tree branches, and when those eggs hatch, the resulting baby cicadas, or nymphs, drop to the ground and burrow into the soil. Depending on their species, they spend 13 or 17 years underground, drinking sap from tree roots, until it’s time for the nearly grown cicadas to emerge.

At some point, the insects are exposed to spores of the fungus Massospora cicadina. It’s not clear to scientists whether it happens when the cicadas enter the soil or when they leave it, or how that exposure happens. This fungus controls the cicadas and ultimately leads to their death.

The spores enter the bodies of cicadas, taking control of them as a fungal parasite. These spores accumulate in the abdomen of the infected cicadas, causing a mass to form. Over time, the back end of the cicada, including its genitals, falls off. In its place, a white fungal plug emerges, containing a cluster of spores bursting out from where the genitals and abdomen used to be. Dr. Matt Kasson, an associate professor at West Virginia University, describes it as resembling a gumdrop surrounded by chalk dust, attached to the rear of these cicadas.

Researchers hold a cicada infected with the fungus Massospora cicadina.

Researchers hold a cicada infected with the fungus Massospora cicadina.

Courtesy Angie Macias/WVU

Infected cicadas, despite having a chalky gumdrop of spores instead of genitals, still try to mate eagerly. The fungus manipulates their behavior, leading to what researchers call hypersexualization. Infected males persist in mating attempts with females and even alter their behavior to attract other males. Female cicadas unaffected by the fungus signal readiness to mate by flicking their wings. Both infected male and female cicadas also flick their wings to attract other amorous cicadas who will soon be infected.

Mating is just one way infected cicadas spread the fungus.

Periodical cicadas have interlocking genitalia. When they pull apart, it causes a rip. This results in a cicada walking around with someone else's genitals stuck to them, as explained by Cooley. The infected cicada is then busted open.

After the chalky fungal plug is ripped apart, the infected and disemboweled cicada flies around, releasing fluffy, brown spores. Kasson refers to them as the "saltshakers of death." These spores spread by the flying saltshakers infect the next generation of cicadas that will emerge over a decade later, continuing the cycle.

An aedes aegypti mosquito is shown under a microscope at the National Environmental Agency's mosquito production facility in Singapore. The photo was taken on August 19, 2020. (REUTERS/Edgar Su)

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Zombie cicadas stimulated by an amphetamine?

It’s quite remarkable how cicadas, despite their bodies being torn apart, continue to move around and mate. Kasson and his team have made an interesting discovery regarding what motivates these insects. "We found amphetamines in the fungal plugs, which could explain why they exhibit this altered behavior," Kasson explained. Amphetamines are known for their strong stimulant effects on humans.

Cooley pointed out that while amphetamines can stimulate the central nervous systems of vertebrate animals, insects like cicadas have a different type of nervous system since they are invertebrates. It remains uncertain whether these stimulants would have the same impact on them.

"We're facing a dilemma here. The fungus is producing a strong psychoactive chemical, but it may not affect the insects," according to Cooley. He proposed that the fungus could be using a different method to control the behavior of cicadas, and the amphetamines it generates could be a defense mechanism against predators like birds that feed on cicadas (and consequently, on the fungus living on cicadas).

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This spring, something interesting is happening with the periodical cicadas. Two different broods will be emerging at the same time in nearby areas. In northern Illinois, the 17-year cicadas will be coming out, while in the Midwest and Southeast, the 13-year cicadas will also make an appearance. It's been a long time since both broods were seen together, not since 1803. But scientists believe that there won't be much overlap in where the two broods emerge.

Kasson is excited to look into the infected insects from both the 17-year and 13-year broods. He wants to find out if there are any genetic differences between the M. cicadina infecting these two different groups of cicadas.

While cicadas are edible, it is important to be selective about which ones you choose to eat. According to Kasson, if you come across adult cicadas that are near the end of their lives or already deceased, it is best not to consume them, even if they are infected with M. cicadina. The small dose of amphetamines in infected cicadas would not affect humans, dogs, or cats if ingested. Additionally, M. cicadina only infects cicadas, specifically the 13- and 17-year varieties, so there is no risk of zombification for humans.

Kasson acknowledges the apprehension people may feel about the impending cicada emergence and the possibility of up to 10% of them developing a grotesque fungal infection. However, he encourages us to view this event as a fascinating biological spectacle and appreciate it as one of the natural wonders of the world.

Kate Golembiewski is a freelance science writer based in Chicago who’s especially interested in zoology, thermodynamics and death.

Editor's P/S:

The article provides a fascinating insight into the bizarre phenomenon of zombie cicadas, controlled by a fungus that hijacks their bodies and behavior. The fungus, Massospora cicadina,