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Confocal Imaging of Scale Development on Butterfly Wings

Both surfaces of the butterfly wing are covered with thousands of colored scales that are arranged in precise linear arrays. Each scale contributes a single color to the overall pattern, which is usually different on the upper and lower surface of the wing. Moreover, the scales have a characteristic surface substructure that is visible using confocal autofluorescence (fig. 1). The ridges on the surface of all of the scales function to control the flow of air across the wing surface during gliding flight, and they contribute to the interference colors in a subset of the scales. The fruit fly Drosophila melanogaster is the closest relative of butterflies for which detailed developmental, genetic and confocal imaging protocols have been established. Specimen preparation techniques for butterfly imaginal discs were largely developed from those for Drosophila tissues. The various stages of butterfly wing development have presented new challenges for confocal imaging. For example, butterfly fifth instar wing imaginal discs are much larger and thicker than those of the fruit fly.