15 Another Look at Spiders

A good many people hate spiders. Few consider that spiders are intelligent, inventive, and good friends to people. Spiders have developed nervous systems. Their brains are capable of remembering, and they are remarkable engineers. They can be found living anywhere from 22,000 feet above sea level, on Mount Everest, to 2,000 feet below the earth's surface, in caves.

The silk that spiders spin for their webs has a strength superior to most flexible products made by humans. These webs have been known to entangle and hold animals as large as mice. The bola spider, instead of making a web, constructs a silken trapper which it hangs from branches or twigs. It attaches a globule of sticky silk to the end of the trapper and casts it out at passing insects. Any insect that sticks to the swinging ball becomes the spider's next meal.

One Ecuadorian species of spider actually travels underwater by carrying a tiny bubble of air with it. Its home is certainly driving bell.

Many scientists feel that without the coy of human life would be in danger. This is because most of a spider's energies are devoted to catching insects. Without spiders, insects would multiply and cover the earth, destroying the vegetation. One estimate says that each year spiders in England destroy a number of insects equal in weight to the human population of that country.

15 重新认识蜘蛛

很多人讨厌蜘蛛，但很少有人意识到蜘蛛聪明、有创造力，还是人类的好朋友。蜘蛛有着发达的神经系统，它们的大脑能记忆，而且是出色的“工程师”。从珠穆朗玛峰海拔22000英尺的高处，到地下2000英尺的洞穴，都能找到蜘蛛的踪迹。

蜘蛛织网用的蛛丝，强度超过人类制造的大多数柔性产品。这些网甚至能缠住并困住老鼠那么大的动物。流星锤蜘蛛不会织网，而是制作一个丝质的“陷阱锤”，挂在树枝上。它会在陷阱锤末端附上一团粘性蛛丝，然后向飞过的昆虫投掷。任何粘在摆动的丝球上的昆虫，都会成为蜘蛛的下一顿美餐。

厄瓜多尔的一种蜘蛛会携带一个小气泡在水下活动，它的“家”就像一个潜水钟。

许多科学家认为，没有蜘蛛的话，人类生活会陷入危险。这是因为蜘蛛的大部分精力都用于捕捉昆虫。如果没有蜘蛛，昆虫会大量繁殖并覆盖地球，摧毁植被。据估计，英国的蜘蛛每年消灭的昆虫重量，相当于该国的人口总重量。