How do you get spiders out of your room?

Hi all!!! I'm switching rooms with my brother and there are a lot of spiders in his room because he has like a underground basement thing (i don't know what its called but theres like a handle to life it up and it goes to under the house). There is carpet on top of it but the still some how et in because the capret is loose and we can't get it perfect. I thought about puting duct tape all over it to block the opening but i can't find any. please answer quick because spiders are my biggest fear