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Sometimes the truth is stranger than fiction.
A new wasp species, discovered in the Ecuadorian Amazon, turns a "social" spider into a zombie-like drone that abandons its colony to meet its demands.
Researchers at the University of British Columbia detail the manipulative relationship between a Zatypota wasp and Anelosimus eximius spider in an article published by the journal Ecological Entomology.
"Wasps manipulating the behavior of spiders have already been observed, but not at such a complex level," said in a statement the principal author of the study, Philippe Fernandez-Fournier, former master student at the Department of Zoology, University of British Columbia. "Not only does this wasp target a species of social spider, but it makes her leave her colony, which she rarely does."
While most spiders are solitary and often aggressive towards other members of their own species, social spiders form relatively durable aggregations.
One of the 25 or so species of common spiders in the world, Anelosimus eximius are known to live in settlements of several thousand individuals, cooperate to capture prey and share parental obligations. According to UBC, insects rarely move away from their basket-shaped nests.
Different stages of the parasitoid wasp on its host social spider (via UBC Science)
Thus, when Fernandez-Fournier noticed that some spiders, infected by a parasitic larva, moved away from their colonies, he took note of it, literally.
"It was very strange because they do not do it normally, so I started taking notes," he said.
He also brought back to the laboratory some of their very dense silk nets and foliage, called "cocoon cloths," intrigued to see what would emerge.
Alert spoiler: It was a wasp.
"These wasps are very elegant and graceful," said Samantha Straus, co-author of the study and PhD student at the University of British Columbia. "But then, they do the most brutal thing."
Looks like they would make good politicians.
By combining data from previous Ecuadorian projects and their own research, the team produced what might look like the plot of a very disgusting horror movie:
After an adult female has laid an egg on the belly of a spider, the larva hatches and attaches to its unfortunate host, the arachnid. He is then likely to feed on the spider-like haemolymph, slowly taking over the body as it grows.
Adult stage of the parasitoid wasp (via UBC Science)
The spider now "zombified" leaves his colony and spins a cocoon for the larva, before patiently waiting to be killed and eaten. After eating, the larva enters its comfortable cocoon and comes out completely formed nine to eleven days later.
Unlike other cases of parasitism, in which wasps target and manipulate solitary spider species, this behavioral change is "so hardcore," according to Straus.
"The wasp completely diverts the behavior and brain of the spider and makes it do something it would never do, like leaving its nest and turn on a completely different structure," she explained. "It's very dangerous for these little spiders."
It is unclear exactly how wasps charmed their victims. Scientists believe that they can inject a dose of hormones into the spider, which could lead to believe that she is at a different stage in her life or run away from home.
"We think wasps are targeting these social spiders because they provide a large stable host colony and a source of food," Straus said. "We also found that the larger the spider colony, the more likely it was that these wasps would target it."
Straus, who now sports a revenge wasp tattoo, plans to continue his investigation in Ecuador on the bizarre behavior of Zatypota and Anelosimus eximius.
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