Fruiting bodies of a cordyceps fungus growing out of the body of an ant, computer illustration. Chains of spores released by the fruiting bodies are visible. Cordyceps is a parasitic fungus that releases airborne spores that infect and slowly destroy the bodies of insects. The fungus can sometimes alter the behaviour of its host before killing it, ensuring the insect will die in a high place, enabling the spores of the fungus to be spread easily.