(A Golden Orb Web Spider with its ant-deterring web; Credit for images: Daiqin Li)
As most homeowners know, ants can be relentless, marching onto property in countless numbers and feasting on anything in sight. They can squeeze through seemingly invisible nooks and crannies in walls, so imagine what it's like for spiders that live out in the open.
One clever species, the Golden Orb Web Spider, deals with this potential ant problem from the outset.
“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,” Daiqin Li, an associate professor in the Department of Biological Sciences at the National University of Singapore, was quoted as saying in a press release.
Li and his team's discovery adds chemical defense to the already impressive properties of spider silk. In addition to its ability to deter ants, silk is unbelievably strong, elastic and adhesive.
The researchers suspected Golden Orb Web Spider silk had this ant-ridding ability for one good reason: they hardly ever saw ants on the webs of these spiders. If you study spiders closely, this would get you thinking, and so they did.
Mark Elgar from the University of Melbourne’s Department of Zoology said that the team was impressed by the strength of the ant repellent in the web silk.
“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,” Elgar said.
The scientists found that only large Golden Orb Web Spiders produce the defensive compound, suggesting that the younger, smaller spiders could rely on their thinner web silk to physically prevent ants from being able to climb into their webs.
The researchers proved their suspicions about the chemical ant deterrent by allowing the spiders to spin webs in their laboratory. They then analyzed the compounds in the silk and identified the defensive alkaloid compound.
“The orb spider is potentially vulnerable to attack from groups of ants while sitting in its web waiting for prey, so the chemical defense in web silk may have evolved to not only protect the spider, but to reduce the time and energy that would otherwise be required to chase away invading ants,” explained Elgar.
The Golden Orb Web Spider is typically found in the forests of Australia, Asia, Africa and America. I hope some are hanging around near my home, helping to keep ants at bay. As much as I like ants (check out Mark Moffett's excellent book about them), ants don't usually make great housemates.