Why Don't Spiders Get Stuck In Their Webs?

This mystery has plagued arachnologists for decades. William Eberhard and Daniel Briceno untangle the web question in a paper in the journal Naturwissenschaften. The answer has to do with spiders' oily, hairy legs.

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IRA FLATOW, HOST:

(unintelligible) Flora is still with us for our video...

FLORA LICHTMAN, BYLINE: Still here everyone.

FLATOW: Still here...

(SOUNDBITE OF LAUGHTER)

FLATOW: ...for our Video Pick of the Week. Hi Flora.

LICHTMAN: Hi Ira.

FLATOW: What have you got for us?

LICHTMAN: It sounds like an April Fools' joke.

FLATOW: It does?

LICHTMAN: Yeah. This week's video pick is a sticky mystery: why spiders don't get stuck in their own webs.

FLATOW: Yeah. That - yeah.

LICHTMAN: OK. I mean, this is the kind of thing that's kind - it just amazes me that we didn't know the answer to this. But apparently there was, you know, a study about a hundred years ago, and some people thought that maybe there was an oil on the legs of the spiders. And then other people didn't believe that and thought that the spiders just avoid the sticky parts of the web because it does - it turns out that not the whole web is sticky. I didn't know that, but just the spiral part is the only sticky part of the orb web. The structural lines...

FLATOW: So the spokes are not sticky.

LICHTMAN: The spokes - right, not sticky.

FLATOW: Oh.

LICHTMAN: OK. So Bill Eberhard and colleagues looked into this and found that it's a little bit different than what people had thought. First of all, spiders definitely touch the sticky part of their web all the time, especially when they're constructing it. But he also found that when he looked at the leg of a spider under a dissecting microscope - and if this appeals to you, you can see this on our website - you see these tiny little hairs called setae. And what happens is when a spider touches the sticky line with this hairy leg, as it pulls away, the glue sort of drips down the hairs, and then you have very little surface area between the sticky glue and the spider. So there's not a lot of pull. And this kind of explains mostly why they - and they touch it very delicately. And then there's this one more little fact, which is my favorite part of this study, which is they wash the spider legs. They clean them off and find that they're much stickier. So they do seem to have a kind of oily substance that repels their own glue.

FLATOW: Wow. Wow.

LICHTMAN: But - it was cool.

FLATOW: Yeah.

LICHTMAN: It was a really cool study.

FLATOW: It's a - it's a cool video. It's our Video Pick of the Week up there on our website at sciencefriday.com. And you - just even seeing the spiders moving around.

LICHTMAN: Yeah.

FLATOW: It's a great video.

LICHTMAN: It's really, yeah, it's slowed down so you can see them, and they're quite big in the frame. And, you know, I hadn't spent much time watching a spider construct its web, but it is really fun to watch. And apparently, this, you know, so they've solved this mystery for this type of sticky line, but, of course...

FLATOW: Of course.

LICHTMAN: ...there's another type of sticky line for which...

FLATOW: That's what keeps you happy. There's always the next video.

LICHTMAN: It keeps us going, absolutely.

(SOUNDBITE OF LAUGHTER)

FLATOW: That's Flora's Video Pick of the Week. Thank you, Flora.

LICHTMAN: Thanks, Ira.

FLATOW: Thanks, thanks, everybody.

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