Brain Eating Fungus
"I think of them then as chimeras: part ant and part fungus," said David Hughes, an entomologist at Pennsylvania State University who was leading the study group, "As time goes on, the fungal part increases until that ant's behavior is no longer its own."
A fungus that is found in Thailand makes ants become infected and act abnormally before eating their brains and oozing out of their dead bodies.
"This so-called zombie or brain-manipulating fungus alters the behaviors of the ant host, causing it to die in an exposed position, typically clinging onto and biting the adaxial surface of shrub leaves," the study authors write.
"In order to get through the exoskeleton, the fungus builds up a pressure," said Hughes. "We know from studies of fungal parasites of plants, particularly rice, they can build up a pressure inside their spore equivalent to the pressure in the wheel of a 747. So they have a massive buildup of pressure, and when that’s at a sufficient level then they blow a hole through the wall and blow all the genetic material into the ant."
"The fungus needs to transmit,” said Hughes, “and it cannot do that inside the nest, because in order for ant societies to work, they have necessarily evolved a prophylactic immune system, which is reliant upon behavioral defense. So they have something called social immunity. They simply stop diseases spreading inside their nest by finding diseased individuals and moving them out."
The ants which had been infected by the fungi were zombie-like in behaviour which gave them the nick names "zombi ants". Well that and giving directors the best plot for a horror movie in existence: Rise of the Ants.