Kefke
Steampunker
This seems like a pretty darn good suggestion, and the sprites look good too. My one quibble, if I were to raise any, would probably be with the boss material. Chitin Plating just seems too plain. Now, follow some flawed logic of mine for a moment. One place that butterflies (and I believe moths as well) have chitinous "scales" like those shown is on their wings. These "scales" are so fine that they leave a dusty residue when the wings are touched. What else resembles a dusty residue? Spores, something closely related to the Contagion. So, I'd suggest making the boss drop match more closely with the wing colour than the body, making it look a bit more "infected", and calling it something that captures that, like "Chitinous Spores".