Deep in the rainforest of Ecuador, a tiny zombie apocalypse is taking place. Zombified spiders are drifting away from their colonies, building strange silk cocoons, and expiring on the forest floor. And it's all thanks to a wasp that’s controlling their minds.

Zoologists from the University of British Columbia have discovered a new species of parasitoid wasp belonging to the Zatypota genus. They found that it employs unsuspecting spiders to complete its life cycle, manipulating their behavior in the process. The findings are published in the journal Ecological Entomology.

The unfortunate spider species is a social arachnid known as Anelosimus eximius. The idea of spiders being social might sound strange, but much like Aragog and his crew from Harry Potter, A.eximius live in large groups. They hunt together, share parenting duties, and rarely stray from their giant webby nests. That is, until Zatypota comes along.    

“Wasps manipulating the behavior of spiders has been observed before, but not at a level as complex as this,” said lead study author Philippe Fernandez-Fournier in a statement. “Not only is this wasp targeting a social species of spider but it’s making it leave its colony, which it rarely does.”

While studying other parasites that live in the spiders’ nests, Fernandez-Fournier noticed some very strange behavior. Some of the spiders were wandering off on their own and building little structures from silk and foliage.

The strange creations were “cocoon webs”, so Fernandez-Fournier – who now sports a tattoo of his discovery – waited to see what might emerge. But rather than a spider, out came a wasp. The team then managed to work out the details of the wasp’s strange life cycle.

First, an adult female lays an egg in a spider’s abdomen. A larva then hatches and attaches itself to the spider. It feeds on the spider’s blood (known as hemolymph) to fatten itself up and eventually takes over the spider’s body, turning it into a zombified version of its former self. The spider then leaves its colony and spins a cocoon web. The parasite continues to feed on the spider until it dies, before entering its snuggly new cocoon. Nine to 11 days later, a fully formed wasp emerges to start the whole grim cycle all over again.

“These wasps are very elegant looking and graceful,” said co-author Samantha Straus. “But then they do the most brutal thing.”

The researchers aren’t sure exactly how the wasps control the spiders’ behavior, but they think they might inject them with hormones.  

If the gruesome tale of Zatypota wasn’t enough for you, check out this wasp that turns cockroaches into zombie slaves, or this one that eats its host from the inside out before sawing itself free.