Lyric discussion by leeroyf2 

Cover art for Needles lyrics by System of a Down

Alright -serj is an amazing artist on youtube he says this song is about your subconscious and along the lines of tapeworms being the dark side of our consciousness.

This is the correct meaning. It IS to do with Filth. At the end of the book Bruce (the anti-Hero) becomes over-whelmed by the Tapeworm who represents the evil within Bruce's concious. Though-out the book it pushes Bruce to commit horrible deeds. It is hard to tell but through the book Bruce has become accustomed to cocaine use and though it is never a major issue, I belive that at the end being drug deprived his tapeworm can take over.