Butterflies possess some of the most striking color displays found in nature. As they fly from flower to flower gathering nectar, their brightly colored wings seem to shimmer and change colors before your eyes. A butterfly’s rich color can act as camouflage, mate attraction, and warning signal. But what is it that makes the bright colors of butterfly wings appear to dance? How can they possess such intense colors?
Butterflies get their colors from two different sources: ordinary color and structural color. The ordinary color comes from normal chemicals that absorb certain wavelengths of light and reflect others. For example, chlorophyll colors plants green. The chlorophyll soaks up the blue and red colors of the spectrum, but not the green, which you see when it bounces back to your eye. Most butterflies get their different shades of brown and yellow from melanin. Melanin is what makes you tan in summer and gives some people freckles.
The structural color of butterflies is where things get interesting. This type of color is from the specific structure of the butterflies’ wings. The color can shift as you, the observer, moves. This effect is known as iridescence. Mother of pearl seashells, fish, and peacocks are just a few examples of animals that have iridescence. You can also see it in soap bubbles. It happens when light passes through a transparent, multilayered surface and is reflected more than once. The multiple reflections intensify the colors.
Butterfly wings, however, are unique. Their wings increase the effects of iridescence because they have many more layers for the light to pass through. This means that there are many more opportunities for the light waves to reflect and magnify each other.
As small as they are, butterfly wings are covered by thousands of microscopic scales, split into two to three layers. Each scale has multiple layers separated by air. When light hits the different layers of the butterfly wing, it is reflected numerous times. The combination of all these reflections causes the very intense colors that you see in many species.
The combination of a butterfly’s structural and pigmented color can create interesting effects. For example, if you saw a butterfly with yellow color underneath a structure that creates a blue iridescent color, you might see green, made by the combination of the two colors. You might also see blue, yellow, green or a combination of the three as the butterfly moves its wings.