Among the piranhas, anacondas, and jaguars of the Ecuadorian Amazon, a newly discovered species of parasitic wasp might be the scariest thing in the jungle.
The wasps “hijack” the brains of spiders known to live in communal webs and force them to abandon their colonies and protect the wasp’s larva for them. Then, the zombie spiders “wait patiently” to be eaten, according to a recent study published in Ecological Entomology.
Researchers specializing in zoology from the University of British Columbia (UBC) documented this bizarre relationship after observing the parasitoid life cycle between the previously undescribed insect in the Zatypota genus of wasp, and the social Anelosimus eximius spider, in Ecuador. A wasp in the Zatypota genus was previously observed modifying the behaviour of a solitary spider, this is the first time a wasp has been found zombifying a so-called “social” spider.
According to the research, after an adult female wasp lays an egg on the abdomen of a spider, the larva hatches and attaches itself to the unlucky arachnid. The larva grows larger and more powerful as it proceeds to feed on the spider’s hemolymph, the equivalent to blood in insects.
Through a behavior-altering process, the larva becomes capable of manipulating the
spider’s decision-making. Host spiders appeared to be “zombified,” according to the study, and would “exit the colony and spin a cocoon for the larva before patiently waiting to be killed and consumed."
Under the protection of the cocoon, the larva feasts on the dead spider and continues to grow. Nine to 11 days later, the larva emerges from the cocoon as a fully formed wasp, ready to go out and zombify another ill-fated spider.
“Once the larva becomes a fully formed wasp, they will go off and find a mate,” co-author Samantha Straus told me in a phone call. “Then the cycle continues.”
For scientists, the brutal methods of parasitoid wasps aren’t a new concept in nature. Creatures that lay their eggs on or in the bodies of other insects and eventually eat them are actually thought to be one of the most diverse animal groups on earth, according to 2018 study published in BMC Ecology. But the newly-identified wasp in the Zatypota genus is unique even among this fearful group.
“This behaviour modification is so hardcore,” said Straus in a UBC news release. “The wasp completely hijacks the spider’s behaviour 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.”
The researchers suspect, that the wasps induce this unusual behaviour in social spiders by injecting hormones into the spider that make it leave its colony and become submissive to the larva.
Additionally, scientists think the wasps are targeting these social spiders because they can
provide a large, stable host colony and food source. They found that wasps were more likely to target larger spider colonies.
Straus says she hopes to return to Ecuador to investigate whether the wasps return to the same spider colonies generation after generation, and if so, what evolutionary advantage that might present.
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