Tuesday, November 3, 2009

Swallowtail Scales

Like most long-established university biology departments, Durham University School of Biological and Biomedical Sciences has substantial collections of specimens that have been donated over the years, including a large number of butterflies ........... which offer an opportunity to explore one the the microscopist’s favourite natural objects – butterfly wing scales. These are the wing scales of a swallowtail Papilio macheon which in this old pinned specimen can't match the vibrancy of colour in the living insect portrayed below, but they are still exquisite objects. If you look closely you can see that they vary in shape as well as colour ... notice how the edges of the red ones are more indented than the blue ones. The metallic colours in butterfly scales are the result of optical effects rather than pigments and are produced by ultra-fine grooves in the scales, where light penetrates to different depths and the reflected light waves interact to produce the electric blue interference colours.

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