The black butterfly symbolises the malfunctioning nature in modern society. It creates and harbours the illusion that butterflies are an infinitely feminine and beautiful creature. Moths are not beautiful, indeed some people are petrified of them, so to make the butterfly black is to shift the focus away from beauty and simply add it into the Addams Family-style dimension of the sinister and bizarre.
Surely, to shift a motif of beauty into the area of gothic fantasy (with or without a sense of humour – I haven’t decided yet) is to replace the meaning of beauty. Replacing the meaning of beauty then in turn questions the area that made the original meaning. And that throws the original premise swiftly down to the abyss of anarchy.