Insect ControlSpiders eat more insects than birds and bats combined, so they should be considered one of human's best friends. They play a big role in controlling insect populations.
Spider SilkSpider silk is incredibly strong and flexible. Some varieties are five times as strong as an equal mass of steel and twice as strong as an equal mass of Kevlar. This has attracted the attention of scientists in a number of applied science fields, but up until recently, humans haven't been able to get much out of this natural resource. It's simply too hard to extract silk from spiders, and each spider has only a small amount of it.
Spiders use their silk in a variety of ways, as we will see below, but Orb weavers are the spiders most of us are familiar with - the type that builds webs in trees and bushes and the corners of our ceilings. When the orb web has deteriorated and is no longer useful, many spider species will destroy it, eating up all the threads so it can recycle the raw silk material. Spiders may leave the heavy bridge thread so that they can easily rebuild the web at a later point.
WeaponryWhile many spiders use their silk to trap their prey, protect their young or build their nests --- the Bolas spider uses it as a range weapon. These spiders do not spin the typical web. Instead, they hunt by using a sticky 'capture blob' of silk on the end of a line, known as a 'bolas'. First, they attract their prey (usually moths or moth flies) with potent pheromones designed specifically for luring their victims. Then, swinging the bolas around and letting it go, the spider may snag its prey rather like a fisherman snagging a fish on a hook.
The Net-Casting spider also uses its web for other than hanging. She will spin little nets that she will then hold with her front legs, suspended above the forest floor, waiting. When she sees her prey, she uses the net exactly as one would trap a cat with a pillowcase.
HydraulicsJumping spiders, one of the more common types of spiders world-wide, have the ability to jump great distances -- as far as 50 times their own length. The thing that is the most amazing about these jumpers is that they don't have particularly strong muscles in their legs; they actually spring forward using hydraulic pressure. A powerful muscle in the cephalothorax squeezes fluids from the body into the legs to make them expand.
With more than 5,000 species around the world, jumping spiders are one of the more common spider varieties around. They're characterized by large eyes, which help them spot potential prey at a good distance. In contrast to web-spinning spiders, most jumping spiders hunt sort of like cats, stalking their prey and then springing on them at high speed.
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