I'm 22, female, and for the last few years i have sporadically had hallucinations in my sleep. always of spiders. i jump out of bed every time...why?

It depends: It depends on what spiders mean to you, what they might signify. It's a good opportunity to explore your life with a psychotherapist to see what this dream means to you. Many types of therapists exist, and finding someone with a jungian orientation might be a good start.

Not hallucination: Seeing things by mr. Y in the absence of an external stimuli and those things cannot be seen by anyone else, is called visual hallucination. In the same way, if ms. X is in her room alone and she starts hearing voices or someone start talking to her, this is auditory hallucination. You cannot have hallucinations, if you are sleeping or dreaming. Ah/vh usually have paranoia or delusions with them.