I first learned about the cordyceps ant attacks when I read Mr. Wilson's Cabinet of Wonders, an outstanding 1996 book about the Museum of Jurassic Technology in Los Angeles. (Such a wonderful book that it's a shame how long it's been since I read it. I have added it to my book-buying queue.)
Among other insanities, author Lawrence Weschler discusses how the cordyceps fungus causes the infected ant to go mad. In a bizarre example of fungal brainwashing, the ant is somehow directed to climb a tall blade of grass, and latch on for dear life. Then the fungus consumes the ant's brain, mummifies its corpse, sprouts from the ant's forehead, and begins releasing spores.