I was watching BBCs ‘Springwatch’ a couple of days ago and Chris Packham mentioned that the colours of butterflies are produced not by pigments but by a special geometric formation of cells, that shimmer and give the illusion of colour. He must have been reading this article published in the June 15th issue of the Proceedings of the National Academy of Sciences (see www.livescience.com/animals/butterfly-wing-colours-100614.html ) where it says that researchers used X-ray scattering methodology to image the wings from two groups of butterflies – in 3-D. They found the wings contain tiny structures called gyroids that diffract sunlight like a crystal. A gyroid is shaped like a stack of boomerangs, each with three blades, that are oriented in alternating directions (hence the shimmering effect). A few days later the story is taken up at http://calderup.wordpress.com by Nigel Calder in what is a very good overview.