Lone Rangers (Spiders)
Despite the evidence of the cobwebs that accumulate in our cellars and gardens, relatively few of the world’s spiders regularly weave webs. Most of them regards it as too laborious and risky a means of trapping their food. Webs give weaving spiders a monopoly of aerial prey, and they positioned them cunningly to take full advantage. But webs are easily broken, and building them exposes spiders to attacks by birds.
Many Spiders rely on their mobility to hunt down food on the ground or to steer clear of danger. The common house spider, for example, is a fast runner, travelling proportionally six times as fast as an Olympic sprinter. Other spider lurk in burrows, trees and buildings until their prey comes to them,. These spiders are invariably more venomous that web-weavers, because they need to overpower their quarry more quickly, instead of leaving it to a lingering death, glued to the larder.
Scientist says that the world’s 40,000 or so species of spider came originally from marine creature that invaded the land some 400 million years ago. Their evolution hasn’t resulted in earlier kinds dying out. Trapdoor and funnel-web spider, for example, have lived almost unchanged in form for millions of years. Ina a process known as adaptive radiation, more and more spiders of different kinds have developed, successfully filling every available ecological niche and porting a wonderful mix lifestyle.
All spiders share predatory habit and unique method of mating. Te male spins a strand of web onto which he drops the sperm. He sucks the web and sperm in to organs known as palps, and then hunts for a female. Swiftly to avoid retaliation and possible injury, he discharges the sperm into her genitals, and makes his gateway. Spiders spin silk by squirting it from modified excretory glands. Originally the silk was used to protect eggs and to line nesting burrows. Now it serves many purposes. As well as webs, it makes trip lines to alert trapdoor spiders to approaching visitors, it wraps up prey: it provides safety lines for jumping spiders, so that if they fall they are suspended by a thread, much as mountaineers are saved by safety ropes. On slender strands of gossamer, hatchlings spiders, which number up to 1000 from one cocoon, can disperse by riding the wind.
Members of the worldwide Theridiidae family spiders, which include the American black widow, lay gum-footed lines on which to catch their food. First, they spin a tangle of web as a anchor, attaching it to the ground, a tree or a rock. Then they stretch a sticky thread to their hideout. An inspecting insect becomes caught on the line, and the spider hauls it in. Net throwing spiders weave a napkin of elastic silk, which they hold with their front four feet as they hang upside down, as their prey approached, they lung, capturing it in the net. The victim struggles serve only to imprison it more tightly. But for originally and simplicity nothing beats the ploys of tropical bolas spiders. The bolas spider dangles a large, sticky globule on the end of a single silk thread. The adhesive attracts moths. The spider senses a moth’s vibrating wings, and swings the lure, like a bolas, faster and faster. When it traps a moth on the sticky bait, the spider hauls it up, like an angler landing fish.
Spider silk is extremely light and strong. A strand stretching from London to New York, a distance of 5536km (3440miles) would weigh less than a pullet’s egg, yet have a breaking strain proportionally greater that that of steel. The silk of the golden orb spider, found worldwide, is the strongest natural fiber known.