If you’re like most people you probably find cobwebs to be a nuisance – something to brush off or wipe away with a dust rag while cleaning house. But it turns out that these messy webs are actually small feats of engineering. Polymer scientists at the University of Akron have discovered that the common house spider can tailor the type of adhesive discs it uses to anchor its webs, making them stronger or weaker depending on where the cobwebs are situated and the anticipated movements of its prey.
Webs located up in the air, such as those on ceilings and vertical surfaces, tend to catch flying insects, which are moving at a greater velocity. So the adhesive used in these is stronger – that way the web doesn’t come loose when it’s struck by an airborne object moving at a high rate of speed. But when spiders build webs that are located close to the ground, they use less adhesive in the discs. When an unsuspecting insect wanders into a web, the anchoring thread snaps away from the ground and – voila! – the spider’s dinner is left dangling helplessly in the air by a sticky silk strand.
The polymer experts were impressed by the sophistication of this trick. “What we have also discovered is a key design principle,” said Ph.D graduate Vasav Sahni. “It’s not a question of the inherent chemistry of the glue, but how the same glue can have different degrees of adhesion.”
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