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Spiderwebs are designed to trap bug-sized creatures. So how come spiders don’t get stuck?

Hosted by: Hank Green
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spider, web, sticky, trap, silk, thread, orb weaver, cocoon, balloon, setae, tarsi, feet, hair, arachnid, coating, sci show, quick question, hank green, science
Hank:  One of my least favorite experiences in all of life is walking into a spider web.  Yeah, I know they're beautiful and they're insanely intricate and wonderful structures, but when, they're on you; they're sticky, and they're touching you everywhere, and you know that one of the things touching you isn't just spider web.  It's the actual spider, but you have no idea which of the thousand places you're being touched is the spider touch.  Just, glauuuch.  Just, sticky death trap all over you.  

Well, they're more than just sticky death traps.  Besides spinning webs to ensnare their prey, spiders use their strong elastic silk threads for lots of things like making cocoons, and making coverings for their eggs and ballooning, which is what it's called when they use a combination of their threads and the wind to blow them to another spot, like tiny, eight-legged hang gliders.  

But, mostly, they're just used to snag tasty snacks.  So, yeah.  Sticky death trap. If it's easy enough for a spider's unwitting prey to get stuck to a web though, why can spiders move so quickly and efficiently around their webs?  Why don't spiders themselves get stuck too?

Actually, there are three reasons.  First, unlike their unsuspecting meals, most spiders don't fling themselves all at once into their own webs, unless they have a death wish.  Instead, they creep carefully across the surface so that only the tiny, bristle like hairs on the tips of their legs, called setae, come in contact with the sticky threads.  Without much of its body touching, it's less likely that the spider will get stuck in its own trap.  

Second, it turns out that a lot of spider webs aren't entirely sticky.  Some arachnids, like the orb weaver, can make non-adhesive threads which serve as a sort of scaffolding for the spider to use to avoid the stickier parts of the web.  Spiders use the hairs and claws on their tarsi, or feet, to grab on to these threads when maneuvering across the capture area of the web.  But no matter how carefully they tiptoe across the web, or whether or not they're able to produce non-sticky strands, most spiders have to, at some point, touch the sticky parts of their webs, especially when they're constructing them.

For years, lots of people thought that spiders had some kind of  oil or a non-sticky coating on their tarsi that protected them from the stickiness of their threads.  But arachnologists, the scientists who study spiders, were never able to prove it and many of them weren't convinced the special coating even existed. 

However, research conducted recently, like 2012 recently, found that certain spiders actually do secrete some kind of special chemical coating that might, indeed, repel their own sticky silk.

 That makes this unnamed substance, which arachnologists still have a lot to learn about, the third thing that keeps these creepy crawlers from sticking to their webs.  So, of course, spiders, they might not spend a lot of time managing internet sites, but I guess you could say that they are in fact, the real web masters.  

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