What does the zombie-making fungus fear? Its own parasite.
Science Tech Daily says in the parasite world, it’s turtles all the way down. No matter how much of a *parasite* you are… like the brain-eating cordyceps fungus, for example… there’s going to be some kind of fearsome parasite that feeds on you:
Ophiocordyceps fungi depend on ants to reproduce and spread. …Eventually, the ant will clamp down onto a leaf, roughly 25 cm off the forest floor, which is optimal for the fungus’ later stage in which it ejects spores onto the soil directly below. The bites are synchronized near noon (possibly cued by clock genes in the fungus) and usually occur in a north-northwestern orientation.
The zombie-ant fungus is not the end of the parasitizing line. It meets its own death at the work of yet another parasite. A secondary fungus, a hyperparasite, can cover the original fungus and its stalk, preventing the fungus from ejecting its spores. The second-level parasite seems to sterilize the spores and these hyperparasites aren’t growing on anything else but the specific parasitizing fungi.
This could explain why the zombie-ant fungus has been so successful over the long term since it could severely damage an ant colony. The presence of a hyperparasite could curb infection rates and keep it in check, creating a sort of equilibrium, keeping it from completely destroying ant colonies.
There are also small insects laying their eggs into the infected ant corpses. Their larvae can eat the growing fungus.