Try to figure out what the spider represents. Do you have a big problem that is hanging over you? A project you are working on and that causes you stress? When I was completing my PhD I regularly had dreams about a Tyrannosaurus Rex (the one from Jurassic Park that chased the Jeep) chasing me making that awful, awful noise. Once I figured out I was stressing about getting my PhD completed – they stopped. No more dreams. Now I dream about even weirder shit and I have no idea what the heck those dreams mean.