A spider's web is obviously disgusting, but it can also be very informational. A spider's web can tell you all about the spider that made it, which type of spider it was being the most important. It can also tell you what kind of other pests are infesting your home. Webs are used for trapping prey, so actual bug specimen may be found in the web. Droppings from other pests might also be found in webs. While that may seem pointless, droppings are very unique from pest to pest. Some research must be done to understand the different shapes and characteristics of droppings, so that they can be identified. Other things that may be found in webs that can provide information include body parts, body shells, and dust, or discarded food stuffs. Below is a video that describes what to look for.
Spider Webs Reveal Other Infestations