Why do spiders spin webs?

Answer

Spider webs are designed to do one thing: catch prey. The size, design, location, and orientation of the web all conspire to capture certain kinds of prey. Not all webs are sticky. Some are made of tangled silk charged with static electricity. “Ladder” webs built by some tropical orb weavers are designed to catch moths. A moth impacts the top of the web, but its slippery wing scales allow it to roll off. The spider’s web is so long, however, that eventually the moth loses most of its scales and is eventually stuck by the time it reaches the bottom of the web. Net-casting spiders in the family Deinopidae suspend themselves over “trails” frequented by insects, and hold a small rectangular web between their front two pairs of legs. When an insect passes underneath, the spider launches itself like a bungy-jumper, sticking the bug to the web and yanking it off the ground. Spiders can even be identified, in many cases, from the kind of web they weave.

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