The Red Admiral butterfly’s living light sensors and signals
We studied the wing colouration and the compound eyes of Red Admiral butterflies with optical methods. The measured reflectance spectra of the wing and scales of Vanessa atalanta could be quantitatively explained by an optical model of overlapping scales stacked on the wing. We utilized the eyeshine in the compound eye of Vanessa indica to determine the spectral and polarization characteristics of its optical sensor units, the ommatidia. Measurements of changes in eyeshine intensity in response to monochromatic stimuli with a novel, large-aperture optophysiological setup and subsequent processing of the assembled images revealed the presence of a random array of three spectrally distinct types of ommatidia. Optical modelling of the rhabdom suggests that the basal photoreceptor has a red-shifted sensitivity, thereby expanding the substrate for butterfly colour vision.
- This article is part of the themed collection: Biological and bio-inspired optics