Switchable reflector in the Panamanian tortoise beetleCharidotella egregia(Chrysomelidae: Cassidinae)

Jean Pol Vigneron, Jacques M. Pasteels, Donald M. Windsor, Zofia Vértesy, Marie Rassart, Thomas Seldrum, Jacques Dumont, Olivier Deparis, Virginie Lousse, László P. Biró, Damien Ertz, Victoria Welch
2007 Physical Review E  
The tortoise beetle Charidotella egregia is able to modify the structural color of its cuticle reversibly, when disturbed by stressful external events. After field observations, measurements of the optical properties in the two main stable color states and scanning electron microscope and transmission electron microscope investigations, a physical mechanism is proposed to explain the color switching of this insect. It is shown that the gold coloration displayed by animals at rest arises from a
more » ... hirped multilayer reflector maintained in a perfect coherent state by the presence of humidity in the porous patches within each layer, while the red color displayed by disturbed animals results from the destruction of this reflector by the expulsion of the liquid from the porous patches, turning the multilayer into a translucent slab that leaves an unobstructed view of the deeper-lying, pigmented red substrate. This mechanism not only explains the change of hue but also the change of scattering mode from specular to diffuse. Quantitative modeling is developed in support of this analysis.
doi:10.1103/physreve.76.031907 pmid:17930271 fatcat:346xrihba5cffkccetuxs5wh7e