OCTOBER 27, 2016 AT 6:00 AM
A zombie crawls through the forest. When it reaches a good spot, it freezes in place. A stalk slowly grows from its head. The stalk then spews out spores that spread, turning others into zombies.
This is no Halloween story about the zombie apocalypse. It’s all true. The zombie isn’t a human, though. It’s an ant. And the stalk that emerges from its head is a fungus. Its spores infect other ants, which lets the zombie cycle begin anew.
KEIZO TAKASUKA
Underneath that worm-like thing is a spider — now a zombie. The wasp larva on its back controls the spider’s brain, forcing it to spin a special web. That new web will protect the larva as it develops into an adult wasp.
In order to grow and spread, this fungus must hijack an ant’s brain. However weird this might seem, it isn’t all that unusual. The natural world is full of zombies under mind control. Zombie spiders and cockroaches babysit developing wasp larvae — until the babies devour them. Zombie fish flip around and dart toward the surface of the water, seeming to beg for birds to eat them. Zombie crickets, beetles and praying mantises drown themselves in water. Zombie rats are drawn to the smell of the pee of cats that may devour them.
All of these “zombies” have one thing in common: parasites. A parasite lives inside or on another creature, known as its host. A parasite may be a fungus, a worm or another tiny creature. All parasites eventually weaken or sicken their hosts. Sometimes, the parasite kills or even eats its host. But death of the host isn’t the freakiest goal. A parasite might get its host to die in a certain place, or be eaten by a certain creature. In order to accomplish these tricks, some parasites have evolved the ability to hack into the host’s brain and influence its behavior in very specific ways.
How do parasites turn insects and other animals into the walking almost-dead? Every parasite has its own method, but the process usually involves altering chemicals within the victim’s brain. Researchers are working hard to identify which chemicals are involved and how they end up so bizarrely altering their host’s behavior