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Scientists exploring the Ecuadorian Amazon have discovered a new parasitic wasp species that turns its victims into zombies.
According to the researchers, diversion is a particularly "hardcore" form of piracy. These wasps first make sure that social spiders turn away from their own colonies, before spinning a cocoon for the larvae that will eat it.
The macabre attack stands out from most other known cases of parasitism by wasps because it is unusual in that it does not target a solitary spider species, as it does. is usually the case.
According to the researchers, diversion is a particularly "hardcore" form of piracy. These wasps first turn the social spiders so that they turn their backs on their own colonies, before spinning a cocoon for the larvae that will eventually eat it.
"Wasps manipulating the behavior of spiders have already been observed, but not at such a complex level," said Philippe Fernandez-Fournier, lead author of the study and former master's student at the Zoology Department of the University of Montreal. 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."
The parasitic wasp originates from the genus Zatypota and targets a spider called Anelosimus eximius – a particularly social spider species, known to live in large colonies and cooperate with others to capture their prey and rear their offspring.
During the research, the team found that some were infected with a parasitic larva and could be seen moving away from their colonies to weave closed canvases.
"It was very strange because they do not do it normally, so I started taking notes," said the researcher.
After taking some of the so-called "cocoon strips" back to the lab, the researcher discovered that there were wasps inside.
"These wasps are very elegant and graceful," said Samantha Straus, co-author of the study and PhD student at the Zoology Department of OBC.
"But then they do the most brutal thing."
The macabre attack stands out from most other known cases of parasitism by wasps because it is unusual in that it does not target a solitary spider species, as it does. is usually the case.
According to the researchers, the adult female wasp first lays an egg on the belly of the spider.
Finally, the larva hatches and attaches to the spider's body, which feeds on it as it grows.
In the zombie state, the spider leaves its colony and creates a cocoon for the larva. Then he expects to be killed and eaten.
The larva emerges nine days later.
WHAT IS A PARASITOID?
Parasitoids are insects whose parasitic larvae eat their host – usually another insect – from within.
They often use a sharp tool called ovipositor to deposit eggs under the skin or an unsuspecting host exoskeleton.
After a short period of gestation, the larvae hatch and begin to consume their host, normally reaching adulthood when the latter is dead.
The parasitoid species are mainly types of bees, wasps and ants, although some fly species also use the macabre technique.
The biology of parasitoids has inspired many science fiction writers and screenwriters to create parasitoid aliens that kill human hosts, including the famous Xenomorph from Ridley Scott's film Alien in 1979.
Parasitoids are insects whose larvae are parasitic and eat their host – usually another insert – from within. In the photo, a parasitic wasp that injects larvae into spiders then sews the host into its nest to fix it
"This behavior change is so difficult," said Straus.
"The wasp completely diverts the spider's behavior and brain and makes it do something it would never do, like leaving its nest and turning into a completely different structure. It's very dangerous for these little spiders.
Researchers have not yet understood how wasps cause spiders to abandon their colonies, although they suspect the use of hormones, which could lead them to believe that they are at a different stage of life .
"We think wasps are targeting these social spiders because they provide a large host colony and a stable food source," Straus said.
"We also found that the larger the spider colony, the more likely it was that these wasps would target it."
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