Meeting Abstract
The wings of butterflies and moths (Lepidoptera) are typically covered with thousands of flat, overlapping scale cells that endow the wings with colorful patterns and make them predominantly impenetrable to light. Yet numerous species of Lepidoptera have evolved transparent wings that allow light to pass through. Transparency requires low absorption and reflection, as well as low scattering of light, and these constraints are often difficult to fulfill for terrestrial organisms. This is particularly due to the large difference between the refractive indices of living tissues (n=1.5) and air (n=1) resulting in significant surface reflections. As a solution, some Lepidoptera have evolved modified scales so that the underlying wing membrane is exposed, and in some cases added elaborate nanostructures on the surface that gradually change the index of refraction and, as a result, give the wing anti-reflective properties. Here we set out to explore the evolutionary history, morphological diversity, and development of wing transparency in Lepidoptera, and find that clearwing traits arose numerous times independently. To probe features of clearwing development, we apply confocal and transmission electron microscopy to generate a description of scale cytoskeletal organization in the glasswing butterfly, Greta oto. Finally, we compile optical and scanning electron microscopy of clearwing scale types and surface nanostructures, highlighting a range of novel and structurally diverse solutions to achieve anti-reflection properties. These findings give us additional insight into the evolution and development of naturally organized micro/nanostructures and may provide bioinspiration for design and engineering of new anti-reflective materials.
