Which fungus alters the behaviour of ants before killing them?

Ophiocordyceps, which infects a carpenter ant, spends days growing through it, and then drives it to leave the colony, climb to a particular height on the underside of a leaf, and clamp its jaws into the vein in a death grip. The fungus then kills it and grows a stalk out of the head to rain spores onto the trail below.

The height and orientation are consistent enough to be called a signature - around 25 centimetres up, on the north side, in a narrow band of humidity that suits the fungus and not the ant. Fossil leaves from 48 million years ago carry the same distinctive bite marks, so the manipulation is at least that old.

The mechanism is stranger than mind control. A 2017 study reconstructing infected ants in three dimensions found fungal cells wrapped around and through every muscle, with the brain itself untouched - so it appears to be operating the body directly rather than issuing instructions to it. Healthy ants recognise an infected nestmate and carry it away from the colony, which is a form of social immunity, and the whole arrangement is what the video game and television series drew on, with the crucial fiction being that it could jump to a mammal.