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1 May 2010 / Liz Johns

Have You Ever Seen A Spider Stuck In Its Own Web?

I was listening to a podcast the other day. The show was Dr Karl – Up All Night, a superbly informative chat show answering the laymans’ queries about science, nature and everything in between. One such question was posed by a caller who asked – why is it that spiders don’t stick to their own webs? The answer that was given thrilled me.

Why is it, why is it? … A spider’s web is made up of sticky and non-sticky threads. The spiders know (somehow) which are which and carefully tread the non-sticky threads, whilst the unfortunate flies don’t know and have a 50-50 chance of getting stuck. Brilliant – I thought. Spiders have developed an ability, something that our scientists have yet to discover, that enable them to recognize sticky from non-sticky. Maybe they can see the sticky threads, maybe they can smell them. Intrigued by this podcast snippet of information I decided to do some research (or more commonly known as – ‘having a quick look on the net’) to find out anything more about this spidery trickery.

Not Really Spidery Trickery

What I found out wasn’t quite as exciting as Dr Karl’s answer made it out to be. A spider doesn’t have any ability to ‘know’ the difference between sticky and non-sticky, I was most disappointed to discover. It is true that there are sticky and non-sticky threads in a web (the hub, the radial spokes and the main thread from which the web hangs are the non-sticky ones) but the key feature is that a spider has claws at the ends of its feet. Two of these claws are used to grip the web so that the spider can pull itself along, the third is used to grasp the thread and pull it away to detach the leg from the sticky thread. All this happening at a tremendous speed to allow the spider to flit across its web eagerly to greet its sadly trapped dinner. There was another theory about spiders secreting oil to stop it sticking to the web, but that oil theory doesn’t hold any water (oh how we laughed at that pun).

Now that I’ve learnt a little bit more about spiders, my fascination for those little eight-legged creatures has increased. But no matter how wonderful I think they are (in theory), I still feel that chilling tingle when I see one just that little bit too close to me. If spiders only knew what power they had over most of the human race.

For exquisitely drawn diagrams of a spider’s claw mechanism, go here.

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