There are several kinds of fungus that infect the brains of insects like ants and crickets. Each fungus controls the mind of its host, eventually killing it and sprouting from the bug's brain. Probably the creepiest killer of all is a fungus called Ophiocordyceps.
But first, some background on the whole zombie ant phenomenon. We already knew a few things about how Ophicordycepts turns ants into zombies. We also knew that there are mind-controlling parasites that cause ants' heads to fall off. But now Pennsylvania State University researcher David Hughes has learned a few more weird things about how Ophicordycepts works.
He observed the fungus infecting Thai carpenter ants when they descended from their tree habitats to the forest floor. As the fungus quickly breeds in the ant's brain, it takes over the ant's behavior and also rebuilds its muscle structure. The first sign that an ant is controlled by this fungus is that it refuses to return to its treetop home. Instead, it weaves drunkenly across the forest floor, stumbling over leaves and wandering.
During this time, the fungus is filling the bug's brain and causing its muscles to enter the first stages of what eventually becomes a rigor mortis-like state. Here's the really weird part. Around noon, all the ants who are currently infected find a leaf and bite down on the leaf's thick, central vein. The muscles in the ant's jaw have been reengineered by the fungus so that they are only able to bite down - the muscles for opening it have atrophied so much that the poor bug is stuck with its jaws clamped shut on the leaf. And the rest of its muscles have gone rigid too.
But the ant doesn't die yet. It clings in this paralyzed, rigid state to the leaf, going even more insane as the fungus grows inside its brain. And then, when night falls, the fungus finally bursts out of the ant's skull and puts the creature out of its misery. The fungus quickly grows into a long, graceful stalk, and thanks to ant mind control, Ophicordycepts is exactly where it wants to be: on the forest floor, attached securely to a leaf.
But why do the ants always bite at noon?
Researcher Hughes told Live Science:
Synchronized arrival of zombie ants at the graveyards is a remarkable phenomenon. It adds a layer of complexity on what is already an impressive feat. However, although ants bite at noon they don't in fact die until sunset. Likely this strategy ensures (the fungus) has a long cool night ahead of it during which time it can literally burst out of the ant's head to begin the growth of the spore-releasing stalk.
Hughes also said that he expects to find "a similar phenomenon" in many other organisms as well. Just remember: The zombie bites at noon!
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Photos by David Hughes