You must first understand that spiders are not insects. They have eight legs, not six, and the head and thorax are one. A spider is thus in two parts, firstly the head and thorax, and secondly the rest of the body which is much larger than the first part. All spiders produce a fine thread from the back of their bodies, though some species can not spin webs. Many leave a constant thread wherever they go, from which they suspend themselves when they move. Others construct a very complicated trap: the first line of a web is the very important suspension line, then other lines are attached. Then the real web begins to take shape. After fixing its support lines, the spider joins them up with more thread, making the characteristic web shape. This is not perfectly circular because the radiating lines join on to different places which are not at equal distances from the center. What are these webs for? Insects fly into them, become entangled and struggle to escape. Alerted by these vibrations, the spider injects its prey with an anesthetic, ties it up and then eats the intruder.
Ask a Question