A spider web is used for more than merely catching insects; the web is the spider's primary means of communication with the outside world. Human beings understand the world primarily through sight, but the almost-blind spider understands the world primarily through touch and vibration. The signals that are transmitted through the silken threads of the web tell the spider where its trapped prey is located. In addition, the web is used to transmit signals in the delicate matter of courtship and mating. The male spider must to let the female know that he is not a trapped insect!
It may surprise you to hear that not all spiders spin webs. We know of 30,000 different species of spiders; only about half of them spin webs. The others are predatory prowlers who are able to find insect prey without using webs. But even spiders who do not build webs manufacture the special silk of which webs can be made. Some spiders make as many as seven different kinds of silk, of varying thickness, strength, and elasticity The process spiders use to make this silk still mystifies scientists and cannot be duplicated by the best textile or industrial chemists