Ophiocordyceps Unilateris. This parasite manipulates, kills, and takes control of formicine ants in tropical forest ecosystems. A previous report in the Atlantic Forest of Minas Gerais (Brazil) showed that on each of four species of infected carpenter ant (Camponotus), the fungus could be identified by a single stalk protruding from the dorsal neck region of the ant. This stalk contained the sexual structures (stromatal plates) which would then project spores to spread the fungus onto leaves and detritus material, which the carpenter ants would then harvest as a food source and subsequently become infected.
In fact, what we know as Ophiocordyceps is actually an assemblage of different species specific to which variety of host ant is infected.
When the host ant becomes infected, usually by contact of spore holding plant matter, it [the host] suffers from convulsions which force it to fall from the tree on which it lives, and then climb the stem of a neighboring plant. Once it has reached the top, it clamps its mandibles on a tall leaf, and dies. The fungus then grows out of the ant’s exoskeleton, and sprouts a fruiting body. This fruiting body then explodes, releasing millions of spores over the surrounding area.
Perhaps most interestingly, the clamping of the mandibles onto the stem of a leaf leaves a dumbbell shaped mark, one which has been discovered on fossilized plant matter from the Messel pit. This pit has been radiometrically dated to 48 million years ago.
The ants typically clamp to a leaf’s vein ~ 25 cm above the ground, on the northern side of the plant, in an environment with 94-95% humidity and temperatures between 20 and 30 °C.
O. unilateralis has been known to destroy entire ant colonies. In response, ants have evolved the ability to sense that a member of the colony is infected; healthy ants will carry the dying one far away from the colony in order to avoid fungal spore exposure.
Sources: 1 2 3
As a side note, this phenomenon of the “zombie ant” has been taken to the extreme in the video game “The Last of Us,” in which ophiocordyceps begins to infect humans and cause them to become a variety of zombified fungal creatures, all of which are insanelyhard to kill. Damn good game though. And probably a game of the year contender.