Real-Life Zombies

Picture a dark graveyard. From its depths, people rise from the dead. They wander the streets as zombies! Forces beyond their control guide these mindless monsters.

This scene happens only in horror movies. But something just as spooky can take place in real life. The brains of living animals are taken over by weird life-forms. They’re called parasites. They can control their hosts. The hosts become real-life zombies! Parasite’s victims include insects, rodents, and snails.

The nightmare begins when a parasite sneaks into an animal’s body. It steals nutrients from its host to feed itself. Then the parasite creeps into the brain of its victim. It forces the animal to do things. The actions help the parasite. But they harm the host.

Many mind-controlling parasites are made up of only one cell, says Susan Perkins. She studies parasites. She works at the American Museum of Natural History. The museum is in New York City. “It’s creepy how these tiny creatures can change the way their host looks and acts,” she says.

Read on to meet four mind-controlling parasites and their zombie hosts. That’s if you dare!

This ant didn’t grow a horn. That long stalk is part of a parasitic fungus. It invades an ant’s body. Then it leads the insect to its doom.

The takeover starts when a tiny fungus cell lands on the ant. The cell is called a spore. The spore burrows through the insect’s hard outer shell. Cells from the fungus multiply inside the ant’s body. Scientists think the fungus releases substances. They control how the insect acts.

The ant begins to act strangely under the control of the fungus. It leaves its feeding area on the ground. It climbs up onto a branch. It bites down on the branch. That clamps the bug in place. This isn’t for the ant’s benefit. The branch is the perfect spot for the fungus. The fungus is there to find its next victim.

The ant dies within hours. The fungus bursts out of the insect’s body. It releases a shower of spores. That’s bad news for any ants crawling below it. They may become the parasite’s next zombie hosts!

What’s weirder than a slimy snail? How about a snail infested with mind-controlling worms?

These garden snails fell victim to a parasitic flatworm. This happens when snails eat bird poop with flatworm eggs inside (see A Parasite’s Life). Baby flatworms hatch and creep into the snail’s brain. Then they invade its eyes. The parasites make the snail’s eyes look like wiggly caterpillars—a nice snack for birds.

Snails usually avoid well-lit locations, where predators can easily spot them. But zombie snails move out into the open. Scientists think that’s because the parasite releases a chemical that changes how the snail behaves. 

Birds see the tasty-looking eye stalks and bite them off the snail. The worm infects the bird, and the cycle begins again. But for the snail, the worst is over—its eyes grow back!

What’s weirder than a slimy snail? How about a snail infested with mind-controlling worms?

These garden snails fell victim to a parasitic flatworm. This happens when snails eat bird poop. The poop can contain flatworm eggs (see A Parasite’s Life). Baby flatworms hatch. They creep into the snail’s brain. Then they invade its eyes. The parasites make the snail’s eyes look like wiggly caterpillars. They’d make a nice snack for birds.

Snails usually avoid well-lit locations. That’s where predators can easily spot them. But zombie snails move out into the open. Scientists think that’s because of the parasite. It releases a chemical that changes how the snail acts.

Birds see the tasty-looking eye stalks. They bite them off the snail. The worm infects the bird. The cycle begins again. But the worst is over for the snail. Its eyes grow back!

Is this rat out of its mind? Most rats avoid cats so they don’t get eaten. But not rats infested with the microbe Toxoplasma gondii (tok-soh-PLAZ-muh GOHN-dee-eye). Infected rats find the smell of cat urine irresistible. They follow felines around!

Is this rat out of its mind? Most rats avoid cats. They don’t want to get eaten. But not rats infected with Toxoplasma gondii (tok-soh-PLAZ-muh GOHN-dee-eye). The microbe makes rats find the smell of cat urine irresistible. They follow cats around!

This ladybug is protecting a baby insect. But the baby isn’t its own. It’s the larva of a parasitic wasp. It forces ladybugs to guard its young.

The spooky wasp first stings a ladybug. The sting injects an egg. The larva grows inside the bug’s body. It sucks up nutrients from its host.