Their minds are no longer their own, and they lurch forward, compelled to find the perfect place to die. But these zombies aren’t interested in brains — they’re just hosts for a fungus that is driving them toward its preferred location to grow and breed.  

And once carpenter ants in Thailand are infected, there’s no escape. The fungus, Ophiocordyceps unilateralis, turns them into the living dead, driving them down from their nests high in the canopy of the forest and guiding them to the undersides of leaves that sprout up on the northwest side of plants growing on the forest floor. It’s the perfect place to reproduce.

The ant’s final act before it dies is to clamp down on the underside of the leaf with its mandibles.

"The fungus accurately manipulates the infected ants into dying where the parasite prefers to be, by making the ants travel a long way during the last hours of their lives," says David P. Hughes of Harvard University, leader of the study on the phenomenon.

Once the zombie ants are dead, the parasite fungus turns the ants’ innards into sugars that fuel its growth, leaving the muscles that control the mandibles intact so the ant will retain its grip on the underside of the leaf.

Ophiocordyceps unilateralis isn’t the only parasitic fungus that takes over ants’ brains and bodies. The Cordyceps fungus germinates on the external surface of an ant’s exoskeleton, and then enters the ant’s body through the trachea, absorbing its host’s soft tissues but avoiding the major organs.

Cordyceps keeps its ant host alive just long enough to force it to climb a plant and clamp down. Then, the fungus devours the ant's brains and grows up out of its head like some kind of alien.

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