title: Switchable reflector in the Panamanian tortoise beetle Charidotella egregia (Chrysomelidae: Cassidinae).
abstract: 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 chirped 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.
authors.affiliation: Département de Physique, Facultés Universitaires Notre-Dame de la Paix, 61 rue de Bruxelles, B-5000 Namur, Belgium. jean-pol.vigneron@fundp.ac.be
authors.forename: Jean Pol
authors.initials: JP
authors.lastname: Vigneron
authors.forename: Jacques M
authors.initials: JM
authors.lastname: Pasteels
authors.forename: Donald M
authors.initials: DM
authors.lastname: Windsor
authors.forename: Zofia
authors.initials: Z
authors.lastname: Vértesy
authors.forename: Marie
authors.initials: M
authors.lastname: Rassart
authors.forename: Thomas
authors.initials: T
authors.lastname: Seldrum
authors.forename: Jacques
authors.initials: J
authors.lastname: Dumont
authors.forename: Olivier
authors.initials: O
authors.lastname: Deparis
authors.forename: Virginie
authors.initials: V
authors.lastname: Lousse
authors.forename: László P
authors.initials: LP
authors.lastname: Biró
authors.forename: Damien
authors.initials: D
authors.lastname: Ertz
authors.forename: Victoria
authors.initials: V
authors.lastname: Welch
mesh_terms: D000818:Animals; D001517:Coleoptera / Q000033:anatomy & histology*; D006813:Humidity; D008027:Light; D013058:Mass Spectrometry; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D010858:Pigmentation; D016062:Porosity; D012031:Refractometry; D012542:Scattering, Radiation