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Golden orb web spiders use chemical alkaloid on silk to repel ants

By Dave Armstrong - 23 Nov 2011 22:2:0 GMT
Spider 'Repell-Ant'

Golden orb web spider on its 'golden fleece' via Shutterstock

Orb web spiders are the Araneids, named after poor Arachne, that delight children with their design skills, and now engineers for the sheer strength of that silk as strong as Kevlar. The Golden orb web spider is the provider of that silk we all want to use for its amazing properties. It's antipodean, hence its Latin name, and common throughout much of the world. But there is now an even more useful property we can all get into!

The ant is a mischievous soul, beloved of Solomon, but none of his wives. Their ancient kitchens were full of them and so are ours. Huge traps full of bodies can be observed in tropical areas and wherever the woods are too close to your door. The problem has been solved yet again by the biological solution. Young spiders have fewer problems as their silk is light and can't support ants walking over it.

Older and wiser spiders are able to coat an alkaloid on their threads that prevents hordes of ants from raiding the larder, or even eating the owner. As they grow larger, the Golden Orb Web spider coats the web with the repellent and no intruder can pass over. Solomon would have enjoyed that. "The type of chemical deterrent found in the spider silk is known as a pyrrolidine alkaloid, which acts as a predator deterrent in many species of ants, moths and caterpillars," remarked Mark Elgar from Melbourne University's Zoology Dept. The alkaloid is industrial strength, it seems and is widely used in nature.

Two ants

Two ants via Shutterstock

Researchers from Melbourne and NUS (National University of Singapore) published the findings in the journal Proceedings of the Royal Society B today [Wednesday, 23 November 2011]. The main Singapore author, Professor Daiqin Li, who led the team at the National University of Singapore, said that ants rarely occur on the web of orb web spiders, despite their abundance, so his team set out to discover why. Webs were analysed from large spiders and then the alkaloid was tested on ant species.

Asian, African, Australian and even American forests have the Golden orb web spider, Nephila antipodiana, with its golden web. It is 20cm from first to eighth toe, on a 4 cm. Body, but as with all orb-webs, the male is a tiny (0.6cm) in comparison.

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