Why do butterflies and moths have ‘powder’ on their wings?

The ‘powder’ on the wings of moths and butterflies is really a layer of any, colored scales, which overlap each other almost, like the tiles on a roof. If you touch the wings with finger the “powder” is rubbed off, leaving the wing more or less transparent and colorless.

The scales are generally like the shape of a hand tapered off at the wrist, and the whole surface is often grooved or cross-grooved. They are really hollow bags growing from tiny cup joints formed in the outer skin of the wings membranes.

They are either filled with coloring materials, or so minutely grooved and surfaced that they refract light to give off an iridescent color, even though they contain no pigment. The brown, red yellow, white or black scales are pigmented. The blues and greens are iridescent.

Many male butterflies and moths have specially shaped “scent-scales” (androconia). These are long and feather-like or broad and bat-shaped. They contain glands for making scents, which attract the females.