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Feather-legged lace weaver spider kills prey by covering it with toxic silk

A research team has found that a common spider kills its prey with poison but does not inject it into them—instead, it covers them with a web of silk and then covers the silk with regurgitated toxins. In their study in the journal BMC Biology, the group collected several spider samples to study under a microscope in their lab and observed as the spiders killed prey.

To kill their prey with venom, spiders typically bite and then inject venom through their fangs. But one spider has been found to take a completely different approach—covering their prey with silk and regurgitated toxins.

The researchers first noted a drawing in a paper published 94 years ago with a description that suggested the feather-legged lace weaver spider regurgitated its toxin and used it to wet its silk after it was spun and then used the silk as a way to kill its prey. To find out if the description was accurate, the researchers went out into the field (plant shops and greenhouses) and captured multiple specimens of the spider for testing in their lab.

The team placed several of the spiders under a microscope and found they all lacked the venomous glands in the head usually seen in spiders. Instead, they found small, oddly shaped muscles. They also found their fangs lacked ducts for injecting anything at all.

Moving lower, they found that genes for encoding the toxins were highly expressed in the spider's midgut. Testing of the toxin showed it was not the same as those made by other spiders, though injecting it into fruit flies showed it was just as deadly. The researchers suspect the muscles in the head help to push out the toxin.

While feather-legged lace weaver spiders were once considered harmless due to their lack of venom glands, this study confirms that they have an equally effective way of subduing prey. Beyond shedding light on spider evolution, the findings may also pave the way for future research into novel toxins.