Butterflies have a layer of tiny scales on their wings, which contain many special chemical pigment particles. These colorful pigment particles combine together to form colorful patterns on the wings of butterflies.
In addition, there are many horizontal ridges on the scales. The more ridges there are, the more patterns there are on the butterfly's wings. Although the chemical pigments on these scales are gorgeous, they will gradually fade or disappear due to oxidation.
Therefore, sometimes we see that only a transparent film is left on a part of the butterfly's wings.
