Making a web is instinctive for spiders it is like no one teaches birds to make their nest. The web silk is produced in silk glands with the help of the spinnerets(special organs which help spider to choose what kind of thread it wants for the web). Generally, the threads originate as liquid, but they dry fast in the air. The key reason spiders spin webs is to catch their dinner. When it catches an insect in the adhesive strands of its web, it comes near the stuck insect and uses its fangs to inject venom. The venom of spider either kills or paralyzes the prey, permitting the spider to relish its dinner in peace.