In general, spiders produce webs to catch prey because it is an efficient method for them to gather food. They may also serve to protect the spider from predators. They make the webs by producing silk, a sticky substance which is produced from their spinneret glands located at the tip of their abdomen.
Spiders have a variable number of spinneret glands depending on their functions, but most spiders have three pairs. There are spiders with only one pair while others have up to four pairs of spinneret glands.
Each of the spinneret glands generates silk for different purposes. The silk produced to catch prey tends to be sticky, while that used to wrap the prey tends to be finer in texture. Some spiders may produce as many as seven or eight different types of silk in their lifetime.
The silk produced from the spinneret glands is made out of protein and it is used in spinning the spider’s web. This is an energy-consuming process which requires large amounts of protein to achieve. The spider then uses the web to catch prey for food.
Eventually, the web they create loses its stickiness and its ability to catch prey. The spider recycles the silk protein by eating their own web to recoup some of the energy utilized in spinning the web.