Parasitic wasp larva gets more than a meal from its spider host

Insect turns arachnid into a zombie, forces it to build its most protective web

A parasitic wasp larva (pale yellow) forces its host spider to modify its web into a structure that can support a wasp cocoon.   

Keizo Takasuka

Parasitic wasps turn spiders into zombie construction workers.

The wasp Reclinervellus nielseni manipulates a spider’s web-building habits to get a custom-built nursery, Japanese researchers reportin the Aug. 5 Journal of Experimental Biology. In lab observations, the researchers discovered that wasp larvae compel Cyclosa argenteoalba spiders to build webs that resemble those that the spiders use to protect themselves while shedding their exoskeletons.

The spiders build delicate round webs to catch prey. But that changes after an adult R. nielseni wasp stings a spider, paralyzing its victim long enough to lay a single egg on the spider’s body. When the wasp larva hatches, it hijacks the spider’s behavior — maybe through a bite that delivers a chemical cocktail resembling the spider’s natural molting hormones. The spider then begins building a simpler, sturdier web on which the larva creates a cocoon.  

While studying wild-caught, parasitized C. argenteoalba spiders in captivity, the researchers noticed that zombie spiders all follow similar construction patterns and produce similar, simple webs like those used in molting. These stronger webs can support a wasp cocoon.

A zombie spider doesn’t get any gratitude for its work. Once a web is built, the larva sucks the spider dry.

SPIDEY SENSE A parasitic wasp larva forces a spider, shown here at 50 times normal speed, to change its prey-catching web into a stronger, simpler structure that can support a cocoon for the larva.Keizo Takasuka

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