Spiders on my mind

Tom: Ewwwww dad, a spider!
Dad: It's not bothering you, why are you so panicked about spiders all of a sudden?
Tom: Because I can feel them crawling all over my back.
Dad: Doubt it. I think it's in your head.
Tom: Dad! Don't say that, there aren't any spiders in my head.
Dad: Sigh, that's not what I meant.