Feather-Legged Lace Weaver Spider Uses Toxic Silk Instead of Fangs to Kill Its Prey

A small and once-overlooked spider has left scientists baffled with a novel method of killing that goes against the spider's grain. The feather-legged lace weaver spider doesn't bite and isn't venomous; it fabricates a silk web and recoats it with poisonous regurgitate to paralyse its prey. They have no venom glands or stingers, even when examined under a microscope. But when the silk-covered toxins were tested on fruit flies in the laboratory, they were just as lethal, a rare finding that runs counter to ideas about how spiders both hunt and kill.

Feather-Legged Lace Weaver Spider Spins Toxic Silk, Evolving a Venom-Free Way to Kill Prey

As per a BMC Biology report, the research team began their inquiry after noticing a nearly century-old sketch describing a spider that appeared to use toxic silk. To test this assertion, researchers collected lace weaver specimens from greenhouses and plant stores and carefully examined their anatomy and behaviour. Under a magnifying glass, they could see no ducts in the fangs and no venom glands in the head, which spiders and many arthropods use to inject toxins.

Instead, the spiders showed oddly shaped muscles in the head and high toxin-producing gene activity in the midgut. The toxins were chemically distinct from those produced by other spiders. The scientists believe those muscles help the brown recluse take the toxins it's regurgitating and transfer them onto the chevroned threads spun with its spider silk, creating a lethal trap that doesn't require a bite.

This finding indicates that the feather-legged lace weaver has evolved an entirely independent venom release mechanism, which could provide a hint at alternative evolutionary routes in arachnids. It also redefines the biological classification of “harmless” spiders, expanding our understanding of how lethal adaptations may manifest in unexpected ways.

Researchers will now investigate the genetic and chemical identity of the causal toxin. The results may also lead to bioengineering or pest-control advances, based on the spider's unusual approach, previously considered unlikely given the lack of a venom gland.