Oh, I imagined a small being, since most of the animals Monster Borns are based upon are quite large. Aside from bunnies, cats, dogs, etc. I was thinking of a moderate sized frame or a small frame to go with the butterfly-like size. It's wings vary the hair color, like for cats; if their ears are white then their hair is white, etc. 

( .-. This is a very stupid suggestion but...can there wings disappear and then reappear? Like control of metamorphosis, a butterfly starts out as a caterpillar and then for a long amount of time they gain wings.