Not all spiders spin webs, but all spiders do spin silk. Spiders use their silk in many different ways. Web-building spiders weave elaborate silken creations, from the intricate orb web to a dense sheet web, to trap bugs. The funnel-web spider builds a tube as part of its web then hides inside it until a bug lands on the web.
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| This Bola spider uses a silk strand with a sticky end to snag a passing bug. (photo: © Steve Davis from www.whatsthatbug.com) |
Some hunting spiders use their silk like a fishing line. The bolas spider uses a single strand of silk thread with a blob of sticky silk at one end to catch moths. A bolas is a ball attached to a line and used in hunting. The spider hangs the thread from its leg. As a moth approaches, it swings the thread. Once hit by the bolas, the moth is covered with sticky silk and the spider reels in her prey. The trapdoor spider uses its silk to make a hidden trap over its burrow, then waits for an unsuspecting bug to fall into the hole. Spiders use silk to build homes, too. Tarantulas and other spiders that live on the ground will line their burrows with silk. Web-building spiders often make a nest for themselves under leaves.
Female spiders wrap their eggs in a silk sac. The sac protects the eggs from moisture and predators. Some spiders, such as the wolf spider, carry the egg sac with them until the babies hatch. Spiders also wrap their food in silk and store it for later use. If you look at a web, you may see several silk-wrapped insects along one edge of the web.
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| Spiders use silk to wrap their prey after they capture it. (photo © Photographer: Harvieux Agency: Dreamstime) |
Spiders use silk to travel. Many spiders use a dragline as a kind of safety harness. It lets the spider pull itself up and down. The jumping spider uses its dragline to pull itself back up if it misses landing on its prey. Spiderlings cast a strand of silk into the air until it catches a current. Then the small spider is then carried away to a new location, sometimes hundreds of miles away.
Scientists have been trying for a long time to reproduce spider silk. It has unique properties. The silk thread is elastic, so it can be stretched and pulled without breaking. It is stronger than steel. Scientists have thought of several different ways that spider silk could be useful to humans: for surgical thread and artificial ligaments; to make parachutes and body armor; and for ropes and fishing nets. So far, though, scientists haven’t been able to recreate the amazing silk thread of the spider.
You can read more about research on spider silk with the following links:
http://www.sciencedaily.com/releases/2007/04/070405094039.htm
http://www.sciencedaily.com/releases/2006/10/061030183133.htm
Take a closer look at a spider web by collecting one. Read how in the activity page.
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| Spiders use silk to make their egg sacs. (photo ©2005 Photographer: Gumenuk Vitalij Agency:Dreamstime) |
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