Brilliant iridescence of Morpho butterfly wing scales is due to both a thin film lower lamina and a multilayered upper lamina

http://crossmark.crossref.org/dialog/?doi=10.1007/s00359-016-1084-1&domain=pdf

Web End = J Comp Physiol A (2016) 202:381388 DOI 10.1007/s00359-016-1084-1

ORIGINAL PAPER

http://crossmark.crossref.org/dialog/?doi=10.1007/s00359-016-1084-1&domain=pdf

Web End = http://crossmark.crossref.org/dialog/?doi=10.1007/s00359-016-1084-1&domain=pdf

Web End = http://crossmark.crossref.org/dialog/?doi=10.1007/s00359-016-1084-1&domain=pdf

Web End = http://crossmark.crossref.org/dialog/?doi=10.1007/s00359-016-1084-1&domain=pdf

Web End = http://crossmark.crossref.org/dialog/?doi=10.1007/s00359-016-1084-1&domain=pdf

Web End = http://crossmark.crossref.org/dialog/?doi=10.1007/s00359-016-1084-1&domain=pdf

Web End = http://crossmark.crossref.org/dialog/?doi=10.1007/s00359-016-1084-1&domain=pdf

Web End = http://crossmark.crossref.org/dialog/?doi=10.1007/s00359-016-1084-1&domain=pdf

Web End = Brilliant iridescence of Morpho buttery wing scales is due to both a thin lm lower lamina and a multilayered upper lamina

M. A. Giraldo1http://orcid.org/0000-0003-3437-6308

Web End = D. G. Stavenga2

Received: 27 October 2015 / Revised: 19 January 2016 / Accepted: 25 January 2016 / Published online: 12 April 2016 The Author(s) 2016. This article is published with open access at Springerlink.com

Abstract Butteries belonging to the nymphalid subfamily, Morphinae, are famous for their brilliant blue wing coloration and iridescence. These striking optical phenomena are commonly explained as to originate from multilayer reections by the ridges of the wing scales. Because the lower lamina of the scales of related nymphalid butteries, the Nymphalinae, plays a dominant role in the wing coloration, by acting as a thin lm reector, we investigated single blue scales of three characteristic Morpho species: M. epistrophus, M. helenor and M. cypris. The experimental data obtained by spectrophotometry, scatterometry and scanning electron microscopy demonstrated that also in the Morpho genus the lower lamina of both the cover and ground scales acts as an optical thin lm reector, contributing importantly to the blue structural coloration of the wings. Melanin pigment has a contrast-enhancing function in a sub-class of ground scales.

Keywords Microspectrophotometry Scatterometry Animal coloration Nymphalidae Melanin

Introduction

Butteries are generally recognized as the order of insects with a most diverse patterning and coloration. The evolution of the color patterns has been driven by different causes, such as sexual selection, conspecic recognition, camouage, and mimicry. The colors are due to the lattice of scales that cover both sides of the wing substrate and are created by the interaction of light with the scales optical materials (Srinivasarao 1999; Kinoshita et al. 2008). Depending on the structure and/or pigmentation of the scales, different wing areas can have distinct colors (Yoshioka and Kinoshita 2006; Stavenga et al. 2014).

Buttery wing scales generally have a very asymmetric structure and basically consist of two chitin layers. One layer is generally a smooth,...