Black and white and green all over

The rain is making trapping too risky, so I am still sitting here pondering the issue of colour and the absence of blue in moths. When I mentioned E B Ford's marvellous book Moths yesterday, I overlooked one obvious point: guess what colour the moths on the classic Collins New Naturalist cover of the book are? Yes, blue. Ford's discussion of the colour issue led me to his even better book Butterflies, which is also a star of the NN series. Discussing colour there, he points out that the 'green' on the underwings of a number of well-known British butterflies is not actually green but an optical illusion caused by 'an intimate mixture of black and yellow scales.' No actual green ones are present. He cites the underwing of the Orange Tip, which anyone can easily spot in April and May, and the Bath White, which you are only likely to see on holiday in countries such as France, where it is common. I thought I'd look at the underwing of the dead Green-Veined White I featured the other day. Sure enough, I think that the 'green' which the eyes register on a quick glance is indeed an effect and the scales are as Ford suggests. As always, a double click zooms things up on your screen although not, I fear, to microscopic levels.