Oh, that is seriously nasty. The bit about parasites causing the ants to climb up a blade of grass to await predation is especially creepy; cordyceps fungi do a similar thing.
Wikipedia writes:
Some Cordyceps species are able to affect the behavior of their insect host; Cordyceps unilateralis for instance causes ants to climb a plant and attach there before they die, assuring maximal distribution of the spores from the fruiting body that sprouts out of the dead insect's body.
Yuck. Reminds me of a David Cronenberg movie.
Mutate and Survive