I can't really read Japanese, but I wonder if this might help?
http://kotobank.jp/word/妹背
Judging from Google Translate, it seems it means something like a 'couple', or perhaps two people who are very close (possibly related)? …Or something to do with potatoes.
EDIT: Therefore I'd interpret the title of this piece of music as
Spider Lily ~The conclusion of each couple is dawn~, which doesn't really make much sense. Maybe it's something like
Spider Lily ~The story of each couple concludes at dawn~ or something… I could be way off. xD