A fungus that hijacks ants inspired one of the most famous zombie stories on TV

Deep in tropical forests, a parasitic fungus spends its life cycle turning ants into remote-controlled delivery vehicles for its own spores. The fungus is Ophiocordyceps unilateralis, and the behavior it forces on its hosts is precise enough, and eerie enough, that it has become a recurring touchstone for fiction about infections that hijack the mind.

That real biology sits behind the Cordyceps outbreak imagined in HBO’s hit post-apocalyptic drama, which borrowed the fungus’s core trick — a pathogen that seizes control of a host’s body and drives it toward behavior that serves the pathogen, not the host — and transplanted it into a fictional human pandemic.

A Fungus With a Single Goal: Spreading Its Spores

Ophiocordyceps unilateralis has, in essence, one objective: self-propagation and dispersal, according to National Geographic. Researchers believe the fungus begins its life cycle when spores attach to a foraging ant and penetrate its exoskeleton. From there it spreads through the ant’s body while the insect continues to behave normally for a stretch, an incubation period during which infected ants go about their business undetected by nestmates.

That stealth phase is notable because social insects like carpenter ants typically practice what biologists call social immunity, ejecting sick colony members before an infection can spread to the group. Ants appear to lack a mechanism for purging the fungus once infected, according to Charissa de Bekker, a University of Central Florida professor who studies parasite-host interactions, in the National Geographic report.

The Death Grip That Gives the Fungus Away

As the infection progresses, the fungus compels its host to abandon the nest for a more humid microclimate better suited to fungal growth. The ant descends to a specific vantage point roughly ten inches off the ground and clamps its jaws into a leaf vein on the north-facing side of a plant, a fixed behavior researchers call the death grip. The fungus then consumes the ant’s internal tissue until it is ready for its final stage, several days after the host has died, when a fruiting body erupts from the base of the ant’s head and releases spores onto the forest floor below to infect the next generation of ants.

Mind Control Without Touching the Brain

One of the more counterintuitive findings in recent research is that Ophiocordyceps does not appear to invade the ant’s brain at all. Researchers from Pennsylvania State University used fluorescent microscopy to track fungal colonization from the rear of the ant’s abdomen up through its body and found no trace of fungal cells inside the brain itself. Instead, the fungus builds a tubular scaffolding around the ant’s muscle fibers, which suggests it exerts control through bioactive compounds that interfere with the nervous system at the muscular level rather than commandeering the brain directly, de Bekker told National Geographic.

The infection is close to always fatal once established, but the fungus does not aim to convert an entire colony into hosts. Ecological balance requires keeping populations in check, so at any given time only a small number of ants in a colony carry the infection — a pattern de Bekker compared to “almost like a chronic cold” rather than a colony-wide epidemic.

A Wider Family of Body Snatchers

Ophiocordyceps unilateralis is only the best-known member of a much larger group. Scientists have identified more than 200 Ophiocordyceps species capable of infecting hosts across ten insect orders as well as spiders, though not all of them produce the dramatic behavioral manipulation associated with the ant-infecting strains. A related species, O. sinensis, infects ghost moth caterpillars and erupts from the host’s head in a way that has made the resulting fungus-caterpillar combination prized in traditional Tibetan and Chinese medicine.

Other unrelated fungi achieve similar effects through different mechanisms. Entomophthora muscae, whose name translates from Greek as “insect destroyer of the fly,” forces infected flies to climb to a set height and glue themselves to a plant by the mouth in a pose optimized for spore dispersal. Massospora cicadina goes further still, filling cicada hosts with hallucinogenic compounds while part of the insect’s abdomen falls away, and the cicada continues moving despite the damage, again in the service of spreading spores.

Why the Science Resonates Beyond Entomology

Part of what keeps Ophiocordyceps in public conversation is the genuine strangeness of an organism that can steer another creature’s body toward its own reproductive ends without ever touching the part of the body responsible for decision-making. “It definitely speaks to the imagination of both scientists and the general public,” de Bekker said. Researchers studying the fungus have also fielded a recurring question inspired by its fictional afterlife: whether a pathogen like it could ever evolve to manipulate a mammal, let alone a human, a scenario entomologists generally regard as biologically implausible given how differently mammalian nervous systems and immune responses are built compared with an ant’s. For now, the fungus remains a tightly specialized predator of insects — one whose real mechanics turned out strange enough to inspire fiction without needing much embellishment.

This article was produced with the assistance of AI and reviewed by an editor.

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