Advisor:  Catherine Jahncke

SLU Festival of Science 2001 Poster Presentation

 

The wings of the Indonesian papilio blumei butterfly exhibit vivid green iridescence from its most distinguishable markings. This brilliant color has been shown to be independent of pigmentation and attributed to microstructure located on and within the individual wing scales.  Using optical and electron microscopy, we were able to show that the origin of the bright green iridescence was a combination of both blue and yellow light, formed as a result of interference and polarization effects attributed to the scale’s structural design.  Scanning electron microscopy revealed that the scales are comprised of regularly spaced concavities or dimples approximately 10 µm in diameter. Transmission electron microscopy shows that beneath the surface of the scale a system of multilayered films also contributes to the iridescence.  Optical microscopy showed that for normally incident light, the flat regions of the dimple appear yellow while the ridges or sloped slides appear blue.  Evidence for the polarization conversion of blue light was obtained through the use of linear polarizers that when crossed revealed the yellow light to be at complete extinction while the transmission of the blue light remained.  Similar mechanisms of bi-coloration or polarization effects are rare and are primarily observed in insects.