Highly Transparent Wing Without Scales: A Nanosized Protuberance Array Overlaying the Wing Surface

Most lepidopteran wings are mainly composed of transparent cuticular membranes and numerous scales. Since most scales are colored and completely cover the membranes, most lepidopteran wings are opaque. However, the wing of the pellucid hawk moth, Cephonodes hylas, has a large transparent region without scales. Its transparency is much greater than that of the transparent wings of many other insects, such as flies and bees. The transparent region of the Cephonodes wing is overlaid with nanosized protuberances, which are regular hexagonally arranged. This nanosized protuberance array is closely similar to that on the cornea surfaces of some insects, including lepidopterans. Through both an experiment with the scale-up model of the cornea and an experiment with the real wing of C. hylas, the nanosized protuberance array is demonstrated to perform the optical antireflection function. In addition to antireflection, this nanosized protuberance array structure is involved in efficient nutrient absorption in the mammalian intestine, and has high hydrophobicity and bactericidal activity. The cellular basis of this structure is also discussed.