Long before humans walked the Earth, while dinosaurs were still roaming the land, a parasitic fungus hijacked the mind of a young ant. Insidiously, the fungus orchestrated the ant’s demise. The ant never knew what hit it. But 99 million years later, we do.
In two pieces of Cretaceous amber from northern Myanmar, scientists have discovered the oldest direct evidence of parasitic fungi infecting insect hosts. One gruesome fossil preserves a young ant, its body pierced by delicate fungal stalks. The other, just as hardcore, shows a fruiting body bursting from a fly’s head. Frozen in time, the pair offer a rare window into the deep evolutionary history of a group of fungi infamous today for their mind-controlling ways: the Ophiocordyceps.
Fossils of the Mind-Benders
Several types of fungi have developed extraordinary ways to control insects. Among the most remarkable ones are the “zombie ant fungi,” Ophiocordyceps unilateralis, which infect carpenter ants in tropical rainforests. When they infect an unfortunate ant, they completely hijack its nervous system. The ant leaves the nest, becoming a doomed puppet. Compelled by the fungus, it climbs a plant high above the colony, clamping its jaws onto a leaf as hard as it can. The fungus then consumes the ant and emerges grotesquely from its head, spreading the spores down to the rest of the colony, hoping to take over other victims.
It’s not just ants that fall prey to this type of attack. Houseflies, grasshoppers, and spiders can also be infected. This behavior is as impressive as it is macabre, and it’s older than you’d probably imagine. But finding fossilized evidence is extremely hard because soft body parts don’t usually fossilize. In these two specimens, however, the fungal structures are clearly visible, marking some of the oldest fossil records of animal-pathogenic fungi ever discovered.
The two newfound species — Paleoophiocordyceps gerontoformicae and P. ironomyiae — were discovered in mid-Cretaceous Kachin amber, dated to approximately 99 million years ago. The fungal growths, although small, are unmistakable. In one sample, spore-bearing stalks — called sporocarps — emerge from the body of an ant pupa. In the other, a club-like structure juts from a fly’s head. According to the researchers, these represent early relatives of today’s Ophiocordyceps fungi, notorious for turning insects into zombified vectors of their own demise.
How Mind-Controlling Fungi Evolves
The research team traced the lineage of these prehistoric fungi using detailed morphological analysis and evolutionary modeling. Their findings suggest that Ophiocordyceps likely originated around 133 million years ago — earlier than previously estimated.
The ancestors of Paleoophiocordyceps probably began by parasitizing beetles, then later shifted to attacking moths and ants as these insects exploded in diversity during the Cretaceous. It was a time when the world was much different. Beetles diversified and colonized extensively during the Cretaceous period, playing a key role in the pollination of many plants. Bees were still relatively new in the picture.
The fossil ant, found to belong to the extinct genus Gerontoformica, adds another layer of intrigue. Ant larvae typically never leave the nest, so the infection likely began inside the colony. In a scenario echoed in modern ant societies, workers may have dragged the infected pupa away to prevent the spread of disease — only for it to become trapped in sticky resin and fossilized.
Though these fossils are ancient, their implications are very much alive.
Today, Ophiocordyceps fungi continue to shape insect populations in tropical forests. Some manipulate ants to climb vegetation and clamp onto leaves before dying, giving the fungus a high perch to launch its spores. Others infect grasshoppers or flies, orchestrating similarly macabre ends. In every case, the strategy is the same: hijack the host’s behavior to maximize transmission. This evolutionary arms race has been playing out for a hundred million years.
Striking Sophistication
If you’re a bit spooked by these fungi, I don’t blame you. Ophiocordyceps, and very much nightmare material. It’s even inspired apocalyptic stories like The Last of Us. They just called it “Cordyceps” in the Last of US.
But while mind-controlling fungi aren’t likely to jump to humans anytime soon, they’re still a striking example of how parasites can evolve incredible sophistication. These fungi don’t just kill their hosts — they puppet them. They coerce them into sacrificing themselves in a way that’s most beneficial for the fungus, and we still don’t know exactly how they developed this mechanism.
By studying their deep past, scientists can better understand the origins of parasitism, fungal evolution, and the evolution of complex ecological relationships.
Amber, once sticky tree resin, has once again captured more than just prehistoric insects. It has frozen a moment of terror that, for the ant and fly, ended long ago. But the struggles of their descendants, plagued by the same type of fungus, continues.
Journal Reference: Yuhui Zhuang et al, Cretaceous entomopathogenic fungi illuminate the early evolution of insect – fungal associations, Proceedings of the Royal Society B: Biological Sciences (2025). DOI: 10.1098/rspb.2025.0407
