Why Do Butterflies and Moths Have Powdery Wings?
The “powder” on the wings of moths and butterflies is really a layer of tiny, colored scales which overlap each other almost like the tiles on a roof.
If you touch the wing with a 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 wing 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.
The scales have at least four functions, not necessarily on the same butterfly species:
They form patterns of bright colors, sometimes with hidden ultraviolet pattern, that are used as signals to the other sex in attraction for mating.
The bright colors are used to advertise particular butterfly’s bad tastes to predators. This protects them from being eaten.
The scales may form patterns that help the butterflies blend into their background and thus escape being eaten by birds or other animals by background resemblance.
Dark colors formed by the scales can be used by butterflies to soak up warmth from the sun that allows their bodies to warm up to flight temperatures in cool seasons or cool environments since butterflies are cold-blooded.