Why the spider is useful?

well i know i don't,but some people are facinated with them.they aren't the nicest living things,but they are very intresting,i mean look at the facts:they live in a web that they were intelligent enough to weave by thereselves,the catch other insects and such the blood,not eat them whole,and they have 8 legs and eyes.that's pretty incredible.but as i always say:the good Spiders are the dead ones. :)