Lethal Barf 

Most spiders pack venom glands to subdue their prey. Then there is one species that uses a more “gutsy” approach to grabbing its meal. 

Meet the feather-legged lace weaver, an unassuming spider that immobilizes its prey by vomiting toxic juices onto other insects in a novel form of chemical warfare but from the gut.

That’s because this arachnid, native to Europe and Africa and known as Uloborus plumipes, lacks venom glands entirely – a rarity among spiders, researchers at the University of Lausanne in Switzerland reported in a new study. 

The team first stumbled across the idea while reviewing a scientific paper from 1931 with a sketch of a spider regurgitating onto its prey. The discovery prompted them to begin a full-blown investigation into the spider’s hunting tactics, wrote Science News. 

Tracking down specimens from plant shops and garden centers, the researchers confirmed the peculiar feeding style: When a lace weaver snares a victim – usually a small insect – it spins hundreds of meters of silk to cocoon it, then regurgitates digestive toxins all over the unlucky prey. 

Cross-sections of the arachnids’ heads confirmed there were no venom glands and the fangs lacked any ducts to inject venom, ScienceAlert added. 

But lab tests on the spider barf showed that this regurgitated substance is loaded with potent toxins – proteins similar to those found in the venom of more conventionally deadly spiders. 

Though technically not “venom” by definition – since it’s not injected – the toxin-laced vomit is just as lethal.  

“These samples proved highly insecticidal, killing an average of 50 percent of fruit flies within an hour of inoculation,” lead author Giulia Zancolli told myScience.ch, a Swiss portal for research and innovation. 

The team explained that the findings offer clues about how spider venom may have evolved, suggesting that the toxins initially served to digest prey before the U. plumipes adapted them for its hunting strategy. 

“These findings support the hypothesis that Uloboridae spiders have lost their venom apparatus while retaining toxin-like genes,” the authors wrote. “The potent toxicity of their digestive fluids… likely compensate for the absence of venom, ensuring effective prey immobilization and digestion.”