Focusing on the familiar: butterfly wings

It's a while since I've written anything (workload, the evil flu of doom etc etc), so I thought I'd resume service with a look at something that everyone's at least broadly familiar with, even if not in detail - butterfly wings. You may know that the insect order Lepidoptera (butterfles & moths) means 'scaly wing', and that's because the wings are covered in many tiny scales that effectively work like pixels to make up the overall pattern.In December a very fresh looking peacock butterfly Inachis io was roosting in our house, presumably hibernating, so I took a couple of pictures.

Peacock butterfly Inachis io

One of the 'eyes' in the wing pattern - individual scales are clearly visible.

Near the base and front edge of the wing - again you can see individual scales.

I could put the wing under a microscope and get more detail, but I didn't want to disturb the butterfly while it was roosting - instead, there is a light microscope image here, and electron microscope images (which I can't produce!) here (x1000) and here (x5000). The last one is important becuase it shows one way that scale colours are formed.

Browns and blackish colours are formed by melanin pigments in the scales - the same type of pigment that we have in our skin, hair and the irises of our eyes. However in most cases the brighter colours - reds, greens, blues and so on - occur because of iridescence caused by the microstructure scattering light in different wavelengths depending on the precise fine structure. If you have a microscope, the scales brush off easily without damaging the wing (you could use a small soft paintbrush then transfer them to a slide) so why not have a look at the scales - if you don't want to disturb a live butterfly or moth, you can wait until a dead one turns up. Happy scaling...