A touch of glass
When you notice a brightly coloured butterfly wing, what you’re actually seeing is light reflected and scattered off millions of nano-sized scales made of chitin.
The wings of the glasswinged butterfly ( Greta oto) of South and Central America do not have these scales. Light hitting them, therefore, is neither scattered nor absorbed.
Instead of scales, the surfaces are covered in randomly distributed and positioned “nano-pillars”, which disrupt the refractive index between the wing and the surrounding air. This reduces reflection to almost nothing. As a result, the butterfly, as its name suggests, looks like it is made of glass, making it one of the most beautiful insects you might never see, even when it’s right in front of you.