There are over 37 000 known kinds of spiders（蜘蛛）in different shapes and sizes in the world. The largest spiders live in the rain forests of South America and are known as the "bird-eating" spiders. These spiders can grow up to 28cm long and they eat small birds. The smallest spiders are from Western Samoa. These tiny spiders are less than 0.5mm long. They live in the plants that grow on mountain rocks.
Some people like to keep spiders as pets but most people don't like touching them. A great number of people are afraid of them mainly because of their poison—something will make them hurt or even die. But in fact, only thirty kinds of spiders are very dangerous to humans. Spiders provide benefits for humans by catching and eating insects such as flies and mosquitoes (蚊子).
Spiders are different from other animals because they make webs to catch the small insects for food. The special silk of a spider's web is light and strong—five times(倍)stronger than steel. Some people have tried to raise spiders in order to collect their silk but no one was successful in doing it. One reason is that it takes 670 000 spiders to produce half a kilo of silk and all of these spiders need living insects for their food. Besides, spiders are usually solitary (独自的) animals and they need keeping alone.
All in all people are amazed to learn that there are so many secrets in spiders!
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