Glass scales on the wing of the swordtail butterfly Graphium sarpedon act as thin film polarizing reflectors

Doekele G. Stavenga*, Atsuko Matsushita, Kentaro Arikawa, Hein L. Leertouwer, Bodo D. Wilts

*Corresponding author for this work

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    The wings of the swordtail butterfly Graphium sarpedon (the Common Bluebottle) have blue/green-colored patches that are covered on the underside by two types of scales: white and glass scales. Transmission and scanning electron microscopy revealed that the white scales are classically structured: the upper lamina, with prominent ridges and large open windows, is well separated by trabeculae from a flat, continuous lower lamina. In the glass scales, the upper lamina, with inconspicuous ridges and windows, is almost flat and closely apposed to the equally flat lower lamina. The glass scales thus approximate ideal thin films, in agreement with the observation that they reflect light directionally and are iridescent. Reflectance and transmittance spectra measured from the glass scales with a microspectrophotometer agree with spectra calculated for an ideal non-absorbing thin film. Imaging scatterometry of single, isolated glass scales demonstrated that the reflected light can be strongly polarized, indicating that they function as polarizing reflectors.

    Original languageEnglish
    Pages (from-to)657-662
    Number of pages6
    JournalJournal of Experimental Biology
    Issue number4
    Publication statusPublished - Feb-2012


    • iridescence
    • wing coloration
    • imaging scatterometry
    • microspectrophotometry
    • Papilionidae
    • LIGHT

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