Delicious. Of course, I don't really eat them. I drink them - drink their blood. I love blood.

July 8, 2007 5:16 AM

How do spiders construct webs between two distant, separate points?

Good Day, Brave Answerers of Metafilter.

Just how do spiders connect a line of thread between two separate points, e.g. between the middle of two tree trunks or posts, with nothing joining them above ground level?

Our theories include the spider floats out on a line of thread (which some spiders do at birth, I believe).

Or, that they anchor one end, drop down, walk across, then up the other structure, then anchor the other end.

I don't think the latter is plausible as I don't think a spider could either retract the excess thread (like a power cord in a vacuum cleaner), or that it could pull up the excess in loops and use it for the rest of the web. I'm assuming that the stickyness of the web silk would prevent it being re-used.

The former would be quite hit-and-miss as the spider can't control where it floats to.

Additionally, how does it know that the two points it starts and ends at are going to make an efficient web?

posted by snailer to science & nature (14 comments total)

From what I've seen they use the wind, with which Wikipedia agrees:
The spider effectively utilizes the wind to carry its initial adhesive thread. With some luck the silk is released from its spinners and carried by the wind to a suitable adherable surface. When it sticks to a surface the spider will carefully walk over the thread and strengthen it with a second thread for added strength.

It is hit and miss, but webs are usually not large enough (between branches of the same shrub, for eg) for it to be an issue.
posted by goo at 5:45 AM on July 8, 2007

Here's another site concurring, specifically talking about orb spiders.
posted by goo at 5:46 AM on July 8, 2007

Ooh, this page is good, showing that some spiders walk down the first and up the second vertical before affixing the web. Interesting!
posted by goo at 5:51 AM on July 8, 2007

goo's answer agrees with everything I have ever seen. They work by instinct, of course, and there is an element of luck. It's not important that the web be built on a specific set of branches. And you never see a failed web because, well, it doesn't exist.

A related animal-ish thing which may further illuminate this method: I used to have a pet iguana named Rapunzel. One breathtaking thing they do is leap from branch to branch in the jungle. However, Rapunzel would often leap from her perch in her habitat smack into the plexiglass wall. I wondered how she could be so stupid when her kin in the wild were so graceful. I found out that they are actually all stupid. When an iguana leaps from its branch in the jungle, it has no idea where it will land; it's just that the odds are it will hit a branch to land on. I think the same is true for spiders. They jump with the wind, and wherever they land, that's where the web starts.
posted by The Deej at 5:52 AM on July 8, 2007

I've often wondered this. Just last week, while walking along a fire road high in the Korean hills trying to find a hiking trail, I came across a spider web that spanned the entire width of the road, at least 15 feet. The actual "web" was only about two feet wide but it was anchored on both sides by single threads spanning the rest of the road. I was totally amazed by it and stood there for a good five minutes looking.
posted by Brittanie at 6:12 AM on July 8, 2007

The stickyness of spiderwebs can be turned on and off, at will, by spiders as they spin it.
posted by the Real Dan at 9:36 AM on July 8, 2007

But did you ever see the results of the LSD they gave Orb spiders in the 50? 60? (God it's years since I read this) but the webs were hilarious. All over the place.

So yes, I have seen failed webs, but it was all in the interests of science so that's OK then.
posted by Wilder at 9:45 AM on July 8, 2007

Well... they weren't failed, exactly. They were just... "alternatively successful."
posted by The Deej at 10:11 AM on July 8, 2007 [2 favorites has favorites]

But did you ever see the results of the LSD they gave Orb spiders in the 50? 60? (God it's years since I read this) but the webs were hilarious. All over the place.

http://www.youtube.com/watch?v=sHzdsFiBbFc
posted by Solomon at 11:22 AM on July 8, 2007 [1 favorite has favorites]

http://www.youtube.com/watch?v=sHzdsFiBbFc [clickable of above link]
posted by churl at 2:34 PM on July 8, 2007

From what I understand, goo's dead on.
Think flying a kite.
posted by The Esteemed Doctor Bunsen Honeydew at 3:35 PM on July 8, 2007

As I understand it, they do both. I'm not sure if it depends on the spider species or location, but some will make the long walk, and others will use a loop of web to catch the breeze.

No problem with the walkers 'reeling in' the excess, they just eat it. Some spiders also eat all the sticky parts of the web every night before reconstructing it (the non-sticky structural stuff they keep until it falls apart).
posted by pivotal at 9:16 PM on July 8, 2007

No problem with the walkers 'reeling in' the excess, they just eat it.

Now I'm picturing a whole pecking order of spiders, with the "walkers" being at the bottom. Spiders, sailing in the wind, mockingly yelling at the poor spider trudging across the road, dragging his silk. "Hey!!! Hey walker!!! How's the weather down there? Stupid walker! Whattya gonna do when you get to the other side, eat your own web? Stupid web-eating walker!"

Maybe it's just me.
posted by The Deej at 6:07 PM on July 9, 2007

People further up in the thread here have it right: it's wind usually, from what I've heard and read, but walking when needed (with exact process varying by species).

Additionally, how does it know that the two points it starts and ends at are going to make an efficient web?

Life's a gamble, but in habitats where web-building spiders live, the odds are very good that there's some kind of vertical structure near the one the spider's standing on. So the odds of finding a web attachment point are not bad.

Making an efficient web is the really key point: efficient to a spider means "catches enough bugs I can eat." That's the most interesting part: how does a spider pick a good web site for catching prey? There is some evidence that they build webs more in places where there is a higher prey capture rate. There seem to be some environmental cues that the spider picks up on when deciding where to build a web.
posted by Tehanu at 6:58 PM on July 11, 2007