Emerald swallowtail (Papilio palinurus)
Mitutoyo 100x NA 0.70, tube lens: ITL200 (Nikon)
Illumination: Halogen and white(!) LED (Ra>95)
This is a collage of 8 pictures from the very same scale, but different illumination (white light, but different incident angles and different polarization angles). This leads to the brilliant iridescence of that butterfly.
Visit the album to see some colour variants of the scales!
This butterfly is a true master in structural (physical) colors. Oblique light produces blue/aquamarin, direct illumination results in a yellow reflection. Back-illumination yields red/brown. Thus, depending on illumination angle (and polarization) any mixture between yellow and blue can be obtained. In addition to the iridecent scales, there are several "normal scales" with pigment colours from brown to orange, yellow and almost white. If you are interested in the details, here is a nature article explaining this phenomenon:
Vukusic, P., Sambles, J. & Lawrence, C. Colour mixing in wing scales of a butterfly . Nature 404, 457 (2000).
