Spiders use two different kinds of threads to spin their webs. One kind is sticky, and is used to catch the flies and insects spiders like to eat. The other kind of thread is a non-sticky, or silky, thread. It is on the non-sticky threads that the spider walks when it wants to get to different parts of its web.
To make walking on its web’s thread easy, the spider has a special hooked claw at the tip of each of its eight legs. Even if one leg should get caught in a sticky thread, the spider can use its other seven to pull that leg off.
Some scientists also think that the spider has a certain kind of oil on its body which helps keep the web from sticking to the spider.
Spiders can tell the difference in the vibrations in their webs made by a fly, an insect, a dangerous wasp, or even something useless, like a leaf or twig!