Spiders, wasps and zombies perhaps all feature prominently in people’s bad dreams, but a combo of all three? That’s some next-level nightmare fuel—and it actually comes straight out of the creepy-cool real world. CBC News reports that researchers have found a wasp species in Ecuador that turns a certain type of spider into a zombie, forcing it to build an incubation chamber before devouring it.
The discovery was something of an accident. Biologist Philippe Fernandez-Fournier, currently a PhD student at Simon Fraser University, was studying parasites that live in the nests of Anelosimus eximius, one of the world’s few social spiders that hunt collectively and rarely leave their nests. Oddly, one day he noticed one of the gregarious spiders ambling off on its own. He followed, finding that the spider began spinning an unusual cocoon-shaped object. “It was very odd ... so I started taking notes,” he tells the CBC.
Fernandez-Fournier collected some of the weird cocoons and took them to his lab. What emerged were elegant little wasps in the genus Zatypota. Looking at studies conducted between 2012 and 2017, Fernandez-Fournier and his co-authors pieced together the life cycle of the wasp finding that the female wasp lays her eggs on the abdomen of the spider. When the larvae emerge, they attach to the spider and feed on its haemolymph, or the spider version of blood. As the larva grows, it takes control of the spider, directing it to leave its colony and spin the cocoon. The larva than consumes its zombie hostage before tucking itself into its cocoon an emerging as an adult wasp 9 to 11 days later. The gruesome study appears in the journal Ecological Entomology.
Targeting colonies of social spiders makes sense, notes study co-author Samantha Straus of the University of British Columbia in a press release. The researchers believe the large stable populations of Anelosimus eximius spiders is a great hunting ground for the wasps, and found that the larger the spider colony, the more wasps there were.
So why does the wasp need to use a spider to build its cocoon? “The environment in Ecuador is intense,” Straus tells the CBC. “The web is basically a protective cage for the wasp to keep growing.”
But the question most of us have is exactly how do the larvae hijack the wasps. The researchers speculate that the wasp injects the spider with a hormone that causes it to flee its colony or to trick it to thinking it’s in a different life stage.
Turning other animals into obedient zombies is not a new phenomenon, and researchers have found that parasitoid wasps, which have been observed hijacking other spider species and cockroaches, are especially good at zombification. However, this particular relationship is unique.
“[T]his behavior modification is so hardcore,” Straus says. “The wasp completely hijacks the spider’s behavior and brain and makes it do something it would never do, like leave its nest and spinning a completely different structure. That’s very dangerous for these tiny spiders.”
Editor’s Note, December 2, 2018: A previous version of this article incorrectly stated the co-author's first name. Straus' first name is Samantha, not Sarah. The story has been edited to correct that fact.