After the ant death, the fungus began growing hyphae inside the insect’s body; in a few days, the hyphae would emerge from the exoskeleton—"always … from a specific point at the back of the head," write the authors of the study, which was led by Sandra Andersen of the Center for Social Evolution at the University of Copenhagen in Denmark. Within a week, the fungus had grown to about twice the length of the host ant’s body and had started sexual reproduction. Meanwhile, "the ant cuticle is … remodeled into a protective case by reinforcing the weaker parts," and the parts of the fungus inside the ant’s body appear to differentiate into separate functions, write the researchers.
When the fungus releases spores, it creates what the authors describe as "an infectious 'killing field'" about one square meter below the ant body that could infect C. leonardi ants or similar species that are unlucky enough to walk there.
Sound rare? Nature is actually full of zombie creatures doing the dirty work for their clever parasite hosts—a phenomenon known as adaptive parasite manipulation. In Central America, ants that eat bird droppings can end up ingesting a nematode parasite that lays eggs in the ants’ bellies, turns them bright red and rounds them out. The color and shape change leaves the ants looking just like local berries that birds like to eat, thereby passing the parasite onto another bird. And one wasp (the emerald cockroach wasp, or Ampulex compressa) attacks cockroaches with venom that blocks a neurotransmitter that allows the insect to control its own movements. The wasp is then free to lead the walking zombie roach into the wasp's nest—to have it serve as host and food for a wasp larva.