Tarantulas spin webs, but they don't use them to trap their prey like many other spiders do. Instead, they live in them and use them for mating and molting purposes.
Some tarantulas spin lines that reach outside of their webs. When prey walks over those lines, the spider feels the vibrations and can come out to catch it. When they are ready to mate, male tarantulas spin a web and leave their sperm on it. A female tarantula later approaches and lays her eggs on top of it. She then weaves it all up into a cocoon that she guards until the eggs hatch. Tarantulas also weave molting mats, which they use when they shed their exoskeletons.