Spiders dose their webs with poison to keep invading ants at bay

Looks like ants aren't the only insects that actively engage in chemical warfare. An international team of researchers has shown for the first time that golden orb web spiders imbue their web-silk with a potent ingredient that keeps invading ants off their turf.

"We found that large golden orb web spiders add a defensive alkaloid chemical onto the silk, which stops the ants from walking onto the web when they come into contact with it," said researcher Daiqin Li, an expert in animal behavior from the National University of Singapore.

Li and his colleagues published their findings in the latest issue of Proceedings of the Royal Society B. The authors write:

Remaining on, or near, the web exposes the resident spiders to many potential predators, such as ants. Surprisingly, ants are rarely reported foraging on the webs of orb-weaving spiders, despite the formidable capacity of ants to subdue prey and repel enemies, the diversity and abundance of orb-web spiders, and the nutritional value of the web and resident spider.

"The paradox is resolved by this chemical that's found on the silk that keep ants at bay," says Mark Elgar, an evolutionary biologist from the University of Melbourne who co-led the study.

"It's a bit like body odour on a cramped bus on a hot day. It's not going to kill you, but it's certainly going to get you off the bus pretty quickly."

[Proceedings of the Royal Society B via ABC Science]
Top image by Daiqin Li