Has anyone ever watched the Planet Earth series? There's one on jungles and it shows this fungus that affects only a certain organism in certain areas. In this case, it was affecting ants and what happens is it pretty much takes over the ants mind and forces it to climb up a tree as high as it can go. Once it's up there, the ant dies and a fungus grows from the back of the ants head. Once the fungus is fully grown it explodes releasing spores and fall to the ground and the cycle continues. It's pretty crazy stuff.
I don't have YouTube at work but it says this is the clip from Planet Earth: