Morpho butterflies are universally admired for their iridescent blue coloration, which is due to nanostructured wing scales. We performed a comparative study on the coloration of 16 Morpho species, investigating the morphological, spectral and spatial scattering properties of the differently organized wing scales. In numerous previous studies, the bright blue Morpho coloration has been fully attributed to the multi-layered ridges of the cover scales' upper laminae, but we found that the lower laminae of the cover and ground scales play an important additional role, by acting as optical thin film reflectors. We conclude that Morpho coloration is a subtle combination of overlapping pigmented and/or unpigmented scales, multilayer systems, optical thin films and sometimes undulated scale surfaces. Based on the scales' architecture and their organization, five main groups can be distinguished within the genus Morpho, largely agreeing with the accepted phylogeny.
The authors declare no competing or financial interests.
All authors participated in the experiments. M.A.G. and D.G.S. wrote the manuscript, which was approved by all authors.
This study was financially supported by the Air Force Office of Scientific Research/European Office of Aerospace Research and Development (AFOSR/EOARD) [grant FA9550-15-1-0068 to D.G.S.]; a research travel grant from the Universidad de Antioquia [to M.A.G.]; and a EURICA (Erasmus Mundus Action 2 consortium) scholarship [to M.A.G.].
Supplementary information available online at http://jeb.biologists.org/lookup/doi/10.1242/jeb.148726.supplemental
- Received August 25, 2016.
- Accepted October 4, 2016.
- © 2016. Published by The Company of Biologists Ltd