How ‘Zombie’ Parasites Control Their Victims’ Minds

The following is an excerpt from Rise of the Zombie Bugs: The Surprising Science of Parasitic Mind-Control by Mindy Weisberger.

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Rise of the Zombie Bugs: The Surprising Science of Parasitic Mind-Control

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A hand punches through the dirt atop a grave, and a gore-spattered creature pulls itself from the soil. A young woman’s bloodied corpse twitches and reanimates, launching itself teeth-first at the throat of the nearest bystander. Pop idol Michael Jackson turns toward his horrified date and reveals himself as a hollow-cheeked, dead-eyed ghoul before leading a troupe of the undead in the first steps of that iconic “Thriller” dance.

Of all the myriad monsters that lurch through our imaginations and fuel our nightmares, zombies are uniquely fascinating and horrible. They might still look like whoever they were in life, but that resemblance is superficial at best and is usually a gruesome distortion of their former selves. Often their bodies are decaying, battered, hideously maimed, and broken. More dreadful still is how zombification changes their behavior. A zombie is no longer in control of its actions; rather, an external agent has seized control and now pilots its host’s mind and limbs, animating them in a grim imitation of life that extends beyond death.

As horrific as zombies might be, their popularity in recent years is undeniable. The long-running cable TV series The Walking Dead, based on the comic book series of the same name, was one of television’s biggest success stories; its bleak vision of desperate survivors navigating a zombie apocalypse ran for more than a decade, spawned multiple spin-offs, and enthralled many millions of viewers. The HBO adaptation of the popular video game The Last of Us, featuring a fungus that zombifies its human hosts, debuted in January 2023 to critical acclaim and immediately captivated audiences, setting a new viewership record for the cable network. Classic novels have been reimagined with undead monsters, such as Pride and Prejudice and Zombies, penned by Seth Grahame-Smith who also credits the original book’s author, Jane Austen (the book was later adapted for the screen). There are zombie action movies (Army of the Dead), zombie comedies (Shaun of the Dead and The Dead Don’t Die), zombie fare for middle schoolers (the Disney Channel’s Z-O-M-B-I-E-S movies), and zombie romantic comedies, also known as zom-rom-coms (My Boyfriend’s Back, Warm Bodies, Life After Beth, and Lisa Frankenstein). Zombie narratives drive popular video games such as The Last of Us, Resident Evil, Left 4 Dead, and Plants vs. Zombies. There are zombified versions of Marvel’s pantheon of superheroes—including Iron Man, the Hulk, Spider Man, Wolverine, and Ms. Marvel—in the comics series Marvel Zombies.

Zombies have even infiltrated reality television. In August 2023, Netflix debuted Zombieverse, an unscripted zombie-themed show. Set in Seoul, South Korea, the program tasked a group of contestants with surviving a zombie apocalypse by evading costumed zombies roaming the city and escaping to an evacuation ship (if a player was “bitten,” they became a zombie and were eliminated from the competition).

Our fascination with zombies is nothing new; for centuries, people around the world have imagined shambling creatures that are somewhere between living and dead, puppeted by external forces. The notion of powerful individuals controlling others’ bodies and minds, through magical or medicinal means, originated hundreds of years ago in West and Central Africa and then traveled to the Americas with enslaved people. Tales of zombies further evolved in Haiti and were then embellished by people scattered by the African diaspora. Stories of zombification spread even more widely across the globe in the twentieth and twenty-first centuries—initially as tales told in novels and comic books, and then through movies and other types of narrative media.

Such pop culture monsters are firmly fixed in the realm of fiction, but there are true zombies that have been here all along. For millions of years, arthropod zombies skittered, scuttled, and stumbled through diverse habitats across the planet. And they still do so today, piloted by parasites that hijack their hosts’ nervous systems, reshape and distort their bodies in gruesome ways, and compel unnatural behaviors that benefit the parasite and the parasite alone, usually leading to the untimely deaths of the creatures they infect. These real-world zombifiers are small—sometimes microscopic—but the manipulative power they wield over their unfortunate hosts is insidious and absolute. Search just about any habitat where terrestrial invertebrates dwell, and you’ll likely uncover a zombie presence.

In southwestern Brazil, a carpenter ant turns away from its nestmates and treks alone, climbing upward on a leaf, where it clamps its mandibles down tight; when it expires, fungal filaments creep from its limbs and a towering stalk erupts from its head. A female soldier beetle in a Florida meadow dies clinging to a flower. Her abdomen swells and she spreads her wings wide, assuming an alluring pose that invites males to become intimately acquainted with the parasitic fungus that killed her. A tiny, glittering tropical wasp stabs a cockroach directly in its brain, injecting it with chemicals that compel the roach to placidly follow the wasp on a dead-end journey to a tomb, where the roach will be buried and then eaten alive by the wasp’s young. In Central Europe, another species of tiny wasp plunges her stinger into a spider’s mouth, delivering a potent chemical injection; the addled arachnid then spins a cocoon web to protect the wasp mother’s larva, which the spider will shield and defend until it becomes the youngster’s dinner. Near a canal in the Netherlands, tiny worms grow inside a snail until they are large enough for their movements to become visible through the snail’s skin. The infected snail abandons its typical haunts in the undergrowth and creeps out into the open, where it can easily be spotted by hungry birds. Meanwhile, in the mollusk’s swollen eyestalks, the parasitic hitchhikers create pulsing displays of patterns and colors that resemble those of squirming caterpillars, enticing birds to swoop down and eat the snails. The next stage of the worms’ life cycle can then play out in the birds’ guts.

Ant, beetle, roach, spider, and snail are but a few examples of organisms all over the world that fall victim to parasites that manipulate a host’s behavior for their own benefit, while also controlling and wreaking havoc on the hosts’ bodies. By zombifying a host—forcing it to behave in a manner that runs contrary to its natural habits or overrides its normal survival instincts—these parasites gain an advantage in their own struggle for survival. (For the purposes of this book, “zombie bugs” refers to a range of invertebrates: arthropods such as insects, spiders, and millipedes, and one mollusk—snails. Entomologists would argue that the word “bugs” is only accurate when referring to a subset of insects with sucking mouthparts, but I’m leaning on the colloquial, broader interpretation of the word, which is more forgiving and commonly serves as a blanket term for all of the diverse minifauna that creep around our backyards, parks, gardens, and homes. Sorry, entomologists.)

A zombified host might reject its own preference for shaded ground and seek sunlight, climbing to heights that help its fungal controllers disperse their reproductive spores. A host may become overly stimulated and hypersexualized, attempting to mate with males and females alike to share its zombifying infection as widely as possible. It may zealously guard and defend the

young of its zombifying master. While under a parasite’s control, a host may abandon the safety of the leaf-covered forest floor for open ground where predators hunt. It may lose its fear of natural predators. In some instances, it will hurl itself into the nearest body of water to drown—all so that the puppetmaster pulling its strings can then pass from the host’s body into the guts of a different host species, to reproduce.

Some brain-manipulating zombifiers are animals with brains of their own, such as wasps, flies, and even minuscule worms called nematodes that have simple, ring-shaped brains containing most of their body’s neurons. But a zombie-maker doesn’t need to have a brain in order to practice mind-control. Certain types of fungi, viruses, and unicellular organisms without brains (or even nervous systems) can still tinker with a host’s neurochemistry and nudge an infected creature to do their bidding. Fungi have been honing this ability since at least the Eocene epoch. One remarkable fossil, approximately 48 million years old, preserves signs of fungal zombification: scars on a fossilized leaf made by the “death grip” of zombie ants that had climbed to their doom.

Fungal zombifiers frequently end up engulfing their hosts’ corpses, sometimes blanketing them entirely and sprouting multiple spore-bearing pillars and stalks. The sight is so ghastly that it’s infiltrated pop culture zombie lore, with infected humans becoming fungus-sprouting monstrosities. In The Last of Us, humans are horribly transformed by a type of fungus referred to as “Cordyceps.” As it happens, this is an actual fungus genus that has long been associated with parasitizing and manipulating insects (though many of the zombifying species that were originally placed in the Cordyceps genus have since been reclassified under the genus Ophiocordyceps).

Unlike Ophiocordyceps-infected ants, which depart their colonies and seek a lonely leaf or twig after zombification, fictional fungus-infected human zombies become deadly hunters of uninfected humans and are brutal when they catch their prey. The so-called Cordyceps infection turns them into ravening creatures with no memory of their former lives and no recognition of friends or loved ones. They attack anyone who’s uninfected, and their bites transmit the spores so that the parasitic fungus can spread to more hosts.

While that bloodthirsty behavioral quirk doesn’t manifest in actual ant zombies, the physical appearance of late-stage Cordyceps–infected humans in these sci-fi worlds—with webs of fungal threads and bulbous growths sprouting from their bodies and heads—is hauntingly similar to the documented demises of zombified ants and other Ophiocordyceps victims.

Fortunately, real-world zombifying fungi and most other mind-controlling parasites restrict their horrific physical transformations and mind-control to insects and other invertebrates. However, humans may be more vulnerable to certain types of zombification than you may expect. Some species of mind-altering microbes have evolved to wreak havoc on mammalian brains, prompting erratic behaviors that promote transmission of the virus to new hosts. The disease known as rabies, for example, caused by the virus RABV in the Lyssavirus genus and transmitted through bites from infected animals, leads to brain inflammation in humans and other mammals, such as dogs, foxes, bats, and raccoons. It promotes aggressive behavior, which helps spread the virus to more potential hosts.

Another microbe, the single-celled protozoan parasite Toxoplasma gondii, causes the disease toxoplasmosis. Cats are the parasite’s definitive hosts, where it mates and lays its eggs, but T. gondii can lurk and survive in just about any species of bird or mammal—including humans. T. gondii is known to alter the behavior of rodent intermediate hosts such as mice and rats, eroding their fear of cats. This leads to highly risky behavior that increases the likelihood of the rodents being caught and eaten, serving the parasite’s purpose by delivering it exactly where it needs to be in order to reproduce: inside a feline’s guts.

Excerpted from Rise of the Zombie Bugs: The Surprising Science of Parasitic Mind-Control by Mindy Weisberger. Copyright 2025. Published with permission of Johns Hopkins University Press.