English class of SIX YEARS AGO!!! I remember studying this shit.... damnit. I could be off on this....
I remember that we looked carefully at the symbolism in the first stanza: "...invisible worm, ..that files in the night...." It may not neccessarily mean that an actual worm FLIES but that a worm that digs it's way around earth, and that one (not that one = worm) that dares to fly at night in a storm showing heroism/stupidity.
Second stanza...hmm... "has found out thy bed" this does seem like a lover's realm from what witeshark mentioned.... but, of crimson joy....Crimson, red, heart, love.... joy=happiness.
"And his dark secret love...." Betrayal....
Toughy eh?
Dough