Brown butterflies survive cold mountain air according to an article in ScienceNOW, 6 Feb 2003. Lycaenid butterflies living in lowland regions are brilliant iridescent blues but those living above 2,000 metres are a dull brown. French scientists have studied the butterflies with an electron microscope and found the blue is reflected light from tiny holes in the scales of the butterflies which behave like photonic crystals that engineers use in the newly emerging science of photonics (capturing and manipulating photons – particles of light). Brown butterflies don’t have such holes so sunlight is absorbed though the wing scales, making the butterflies appear dark, and is used to keep the wings warm.
Editorial Comment: The presence or absence of holes may be response to the temperature of the environment butterflies are inhabiting. To find out someone would need to breed each butterfly type at the other temperature. Other creatures such as Ptarmigans (a bird) and rabbits produce different colours in response to different climates or seasons. This is not evolution.