Ultraviolet reflection in mayfly wings

Abstract

In the present study it is shown for the first time that the transparent membranous wings of mayflies (Ecdyonurus gr. venosus) can reflect UV light at both the imago and subimago stage. In the imago, reflectance spectra from male and female wings are significantly different with female wing reflection in the UV wavelengths higher than that of males. In the subimago the wing reflectance spectra of both sexes are similar and the intensity of reflection is lower compared to the imago. Higher UV reflection in female wings corresponds to wavelengths of the maximum sensitivity of male compound eye (recorded in other mayfly species), thus making wings a potentially important visual cue for recognition and mating. The UV reflection in the wing of E. gr. venosus is angle dependent, thus revealing its structural nature. Wax crystals in the form of rods in the wings of the imago have an important role in shaping the pattern of the reflectance spectra owing to their omnidirectional antireflection properties. This study can contribute to understand the role of UV light sensitivity as part of the integrated visual system of many animals, a research field so far disregarded owing to our anthropocentric dimension and to unravel the functional role of nanostructures of insect surfaces with special optical properties which can inspire new biomimetic surfaces.

Keywords: Antireflection; Biological optics; Biophotonics; Insects; Mating; Wax.