These fungi control ant behavior with mind-altering chemicals, then kill them. They're part of a large family of fungi that create chemicals that mess with animal nervous systems.

Usually scientists study these fungi as specimens preserved in a lab, said entomologist David Hughes of Pennsylvania State University, co-author of a study March 3 PLoS ONE. "By going into the forest to watch them, we found new micro-structures and behaviors."

Once infected by spores, the...