[jazzyvee]

jazzyvee  asked the Naked Scientists:
   
I have a question about spiders.

This morning I went out to feed the fish in my pond and saw that overnight a spider had made a web across the largest span of the pond between two plants growing on opposite sides.

It's something that has baffled me for years so my question is.
How do spiders construct a web across a large open space, especially in this case across open water?

Thanks

Vince Mills ( Solihull West Midlands)

What do you think?

[LeeE]

They spin a thread of silk and let the wind carry it away from them until it hits and sticks to something.  In this case the spider will have climbed up the plant that was up-wind from the other plant and then let the wind carry the thread across.

Some spiders use a similar technique to migrate, except when they do this they pick a spot where there's nothing downwind of them for the silk to get stuck to, and when they've spun out a long enough thread they let go of whatever they were standing on/holding on to and let the wind carry them off.

[thedoc]

We discussed this question on our show

Helen -  This is particularly relevant because I think there’s been a hatching of spiders in Cambridge very recently.If I sit in my garden for more than about 5 minutes, I get turned into a spider web. So, they're doing it at the moment.

Chris -  Turned into a spider web?

Helen -  Okay. One gets made around me. So they're definitely out there doing this but how are they doing it?

Chris -  Hopefully, it’s a money spider. Yes, a good question, isn’t it? because you think, “I see this web. It goes from one tree over there to one tree over there. did the spider go all the way down, walk along the ground, up the other tree, and then string this piece of thread across the two?” The answer is no, of course. It’s too small to know these places exist relative to each other.
The way the spiders do this actually is that they sit on the end of one twig or something, and they stream out this very long but very light thread of silk which gets picked up on air currents and it floats away from the spider, and the spider is continuously testing the tension in the thread. When it feels it goes taut, it realises it must have snagged on something. So it will then fix that end and go across counting steps - because the spiders measure distance by counting their steps, and it therefore knows how far away it is. It then counts back halfway, knows that it’s halfway back across and then drops a perpendicular. So it goes down to the ground and that’s the middle of its web in a sort of T-shape, and fixes the bottom thread, and then after that, it’s got the three points it needs to start making the web. So that’s how it does it, ingenious stuff.


Click to visit the show page for the podcast in which this question is answered. Alternatively, [chapter podcast=2752 track=10.06.27/Naked_Scientists_Show_10.06.27_6603.mp3] listen to the answer now[/chapter] or [download as MP3]

[Bob Walsh]

it's really wild but I have this spider whos been making a web everyday in about the same spot right by my front door but he makes the web kind of off to the side a little bit so I won't walk into it when I leave or enter my house...this is toward night and the next morning the whole web is gone...but there he is around 8pm making the web again...now this guy has to be about the size of a quarter (that's just his body not his legs)...he's scary but then again I'm amazed at all the work he goes through....last night I saw him building it and I just stood there and watched him work....he just kept going...now tonight he's at it again...it's a shame because I know that tomorrow morning it'll be gone and he'll just have to do it all over again....Bob