One thing I wonder about is - why would it evolve to make the ants go away from the anthill?
Surely it would be best for spreading the fungus to make them go to the anthill and die there?
It seems more like a quarantine mechanism from ants POV. The fungus would spread faster if the ant continued as usual till it died, or stayed in the anthill.
But it also helps the fungus in a way - if the ants died in the anthill the whole anthill would soon die and the fungus with it.
So - maybe the ant reaction to the infection is actually a coevolved compromise between the fungus and the anthill, that lets both survive at the cost of individual ants?
I believe the other ants recognize that the individual is infected and forcibly dispel her from the colony, which is a defense mechanism the ants likely evolved. At least that's what's portrayed in the Planet Earth documentary, which spends a few minutes focusing on this fungus. The fungus could have evolved to be more sneaky so the ants wouldn't recognize the infection until it was too late, but I imagine it's easier to just have the ant go somewhere high up instead.
If I remember correctly, the fungus often (always?) manipulates the insect to climb to a relatively high point before spores burst from its head and body.
Surely it would be best for spreading the fungus to make them go to the anthill and die there?
It seems more like a quarantine mechanism from ants POV. The fungus would spread faster if the ant continued as usual till it died, or stayed in the anthill.
But it also helps the fungus in a way - if the ants died in the anthill the whole anthill would soon die and the fungus with it.
So - maybe the ant reaction to the infection is actually a coevolved compromise between the fungus and the anthill, that lets both survive at the cost of individual ants?