Spider webs are designed to cope with stress and disruption, favouring repair over rebuilding.
With a proposed referendum on Scottish independence likely to happen in 2014, some 700 years after the Scots army triumphed over English forces at the symbolic Battle of Bannockburn, one tale that seems certain to be told in the build-up is the story of Scotland's King Robert the Bruce and the spider. According to legend, Bruce was hiding in a cave in the wake of several defeats when he was inspired to fight again after watching a spider persevere, and eventually succeed, in its repeated attempts to spin a web.
As Bruce — who led the Scots to victory at Bannockburn — discovered, failure does not come easily to a spider. And although the amazing properties of spider silk have fascinated us for generations, the secrets of their webs have remained elusive.
In a paper on page 72 of this issue, Markus Buehler at the Massachusetts Institute of Technology in Cambridge and his colleagues report on perhaps the most impressive design feature of a spider's web: its structural and mechanical strength. In research that both modelled webs and investigated those spun in situ by local garden spiders, the authors found that the strands of silk adapt to the amount of stress they experience, and how that stress is loaded onto them.
Under a light stress, a gentle highland breeze perhaps, the silk softens and extends, so allowing the web to retain its structure. But when a larger and more disruptive force strikes — such as a hand groping for a light switch in a dark attic — the silk strands first extend, then the most stretched of those strands become suddenly rigid and so break. This sacrifice of a strand or two localizes the damage, and keeps the rest of the web intact. Once the disturbance has passed, the spider can scurry out to repair the web, rather than being forced to rebuild. As Bruce — who exploited heavily wooded areas to conceal his preparations for the decisive battle — discovered, it is easier to persevere, and to succeed, when nature is on your side.
These are heady times for arachnophiles. Last month, a stunning shawl and cape woven from spider silk went on display at London's Victoria and Albert Museum. The two garments, which took eight years to create, contain silk produced by more than one million female Madagascan golden orb-weaver spiders, amassed by a team of 80 people. They used long poles to collect the spiders from their webs each day, and harvested their silk before returning them to the wild. The garments are the first textiles to be made from spider silk since a set of bed hangings displayed at the 1900 Paris Exhibition. It is another achievement for the power of perseverance. Or perhaps, as those set to campaign in 2014 for Scotland to remain part of the United Kingdom might stress, it marks a triumph of, and a tribute to, sticking together.
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Damage limitation. Nature 482, 6 (2012). https://doi.org/10.1038/482006a