Cool Butterfly Photonic Crystals
The small structures in the scanning electron microscope image of a
butterfly wing scale (a) are natural photonic crystals that give the
wings of some butterflies their brilliant iridescent blue colors. The
structures in the second image (b) are responsible for a blue-violet
iridescence. In the third image (c), the small structures are almost
entirely absent, and the butterfly wing scales are a dull brown shade.
New research suggests that photonic crystals keep butterfly wings cooler,
as well as making them beautiful. In higher elevations where butterflies
are more reliant on sunlight to keep them warm, some of the insects
have evolved wing scales in which the photonic crystals have been disrupted
(as in image c), improving the chances that they survive long enough
to mate despite the frigid climate.