How Tiny Organisms Control Minds, Create Zombies, and Shape Ecosystems

Miniature zombies are all around us, scuttling through the underbrush or flying through the air in nearly every continent on Earth. In Brazil, a fungus takes over ant brains, altering their circadian rhythms and social behaviors. In England, a virus forces caterpillars to climb high into the canopy, then slowly liquefies their bodies, which drip onto the leaves below. In Indonesia, a parasitoid wasp uses specialized venom to alter a cockroach’s brain chemistry, turning it into the perfect host for her young.

In her new book, Rise of the Zombie Bugs, self-described professional science nerd Mindy Weisberger introduces readers to a menagerie of mind-controlling parasites, and the scientists who have devoted their lives to the study of these peculiar organisms. Through these vivid tales of creatures bizarre enough to rival any fictional beast, Weisberger offers readers a peek into the fields of evolution, ecology, neuroscience, and molecular biology. She shows that these topics exist beyond dim lecture halls and dry textbooks: “Science is everything and everywhere,” she said.

A Late-Blooming Love

Despite her evident passion for the subject today, Weisberger has not always been interested in science. “When I was in film school, I thought I was going to make punk rock music videos,” she said. “It wasn't until I started working for the American Museum of Natural History [AMNH] in the exhibitions department, that I really got this look under the hood of how science works…that was my eureka moment. I thought, ‘Oh, science is actually really cool and interesting. Why did nobody tell me this?’”

Once bitten by the science bug, she never looked back and has worked in science communication for more than two decades. She first learned about a fungus that turned ants into zombies during her work at the AMNH and was immediately enthralled by these real-life versions of horror movie monsters. “These are the types of science stories I've always been drawn to—these examples of really bizarre adaptations, weird behaviors, and relationships that have evolved, in many cases, over millions or even hundreds of millions of years, but to humans, seem like a weird way to live,” said Weisberger.

Like Weisberger’s fascination with science, her Zombie Bugs book also begins in a museum—the Naturalis Biodiversity Center, located in the Netherlands. The museum boasts an impressive collection of dinosaur fossils, millions of butterfly specimens, and an extensive herbarium, but Weisberger isn’t there for them. She’s there to see the many parasites suspended in various types of preserving fluids; she is particularly interested in Leucochloridium, “which is a type of worm that infects snails and causes the disco-eyed zombie snails,” she explained.

While many parasites are content to complete their entire lifecycles inside a single host, Leucochloridium species have evolved a more complex—and horrifying—way of life.¹ Birds infected with these particular parasites excrete Leucochloridium eggs in their droppings, which are picked up by hapless snails. The worm larvae make their way through the snail’s tissues to its eyestalks, where they form broodsacs, pouches that can contain hundreds of individual larvae. Because the worms need to get back into a bird to complete their lifecycle, while the snail host would very much prefer not to be eaten, the worms have developed the ability to alter the behavior of their hosts via as-yet-unknown mechanisms. Worm-infected snails become more active and seem to prefer higher, more brightly lit perches, increasing their accessibility to avian predators. To further tempt the birds, the stripey broodsacs begin to pulse rapidly, giving them the characteristic disco-eyed appearance. Scientists think their strange, pulsing eyestalks mimic the movement of a tasty caterpillar. When a bird takes the bait, the parasites take up residence in its gut, mature into adults, and reproduce, beginning the cycle all over again.

Throughout the book, Weisberger reveals the uncomfortable pervasiveness of this zombie phenomenon: Fruit flies, cicadas, ants, bees, caterpillars, spiders, grasshoppers, and ladybugs can all be victims of these tiny, parasitic puppet masters. “The zombifiers are diverse. The hosts that they zombify are diverse. The mechanisms that they use are very diverse,” said Weisberger. “So individually, all of these examples are really exciting, but together, they also added up to this really interesting picture. Just what is behavior manipulation? Why is this strategy so successful? And why are so many organisms doing it?”

Answering these questions, said Weisberger, is a component of our larger understanding of life on our planet, and how it came to exist in all its weird and wonderful forms. Studying these unusual relationships, and the mechanisms that allow them to operate in such highly calibrated ways, she said, “Is important for understanding how organisms evolve, how they adapt, and the different kinds of lifestyles and pathways that evolution can take.”

Putting Zombie Organisms to Work

Zombie research could also have more concrete applications. Because many of these zombifying agents have fine-tuned their manipulation abilities to the point that they specialize in just one type of host, scientists are exploring how they might be used to develop more ecologically-friendly pest control strategies that target crop pests or invasive species, while sparing bees and other insects that provide important ecosystem services.²

The bioactive compounds produced by zombifying organisms could also be useful in medicine. For example, the emerald cockroach wasp’s venom, which interacts with dopamine receptors in the cockroach brain to influence motor behaviors, could help inspire new treatments for movement disorders such as Parkinson’s disease.³ And Ophiocordyceps unilateralis, the fungus famous for creating zombie ants, produces secondary metabolites that may influence neurological function in mammals.⁴

But it’s not just the science itself that is important—science storytelling itself also plays an important role in shaping minds and societies. “I think people are, by nature, curious,” Weisberger said. “I think that unfortunately, there are a lot of toxic ways that that curiosity can be misdirected. And that's what we're seeing a lot of now.”

Now, more than ever, science communication is crucial. “Basic science literacy is essential for existing in modern society…for understanding how our lives are interconnected, not just with each other, but also with the wider world around us,” said Weisberger. “We've been seeing a lot of active efforts to undermine the public understanding and perception of science. And this is where I think science communication and science storytelling can be really effective—in rebuilding that trust.”