title: Brilliant camouflage: photonic crystals in the diamond weevil, Entimus imperialis.
abstract: The neotropical diamond weevil, Entimus imperialis, is marked by rows of brilliant spots on the overall black elytra. The spots are concave pits with intricate patterns of structural-coloured scales, consisting of large domains of three-dimensional photonic crystals that have a diamond-type structure. Reflectance spectra measured from individual scale domains perfectly match model spectra, calculated with anatomical data and finite-difference time-domain methods. The reflections of single domains are extremely directional (observed with a point source less than 5°), but the special arrangement of the scales in the concave pits significantly broadens the angular distribution of the reflections. The resulting virtually angle-independent green coloration of the weevil closely approximates the colour of a foliaceous background. While the close-distance colourful shininess of E. imperialis may facilitate intersexual recognition, the diffuse green reflectance of the elytra when seen at long-distance provides cryptic camouflage.
authors.affiliation: Computational Physics, Zernike Institute for Advanced Materials, University of Groningen, Groningen 9747AG, The Netherlands. b.d.wilts@rug.nl
authors.forename: Bodo D
authors.initials: BD
authors.lastname: Wilts
authors.forename: Kristel
authors.initials: K
authors.lastname: Michielsen
authors.forename: Jeroen
authors.initials: J
authors.lastname: Kuipers
authors.forename: Hans
authors.initials: H
authors.lastname: De Raedt
authors.forename: Doekele G
authors.initials: DG
authors.lastname: Stavenga
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D001517:Coleoptera / Q000737:chemistry / Q000502:physiology / Q000648:ultrastructure*; D003198:Computer Simulation; D003460:Crystallization; D046529:Microscopy, Electron, Transmission; D017785:Photons; D010858:Pigmentation; D012031:Refractometry; D014921:Wings, Animal / Q000737:chemistry / Q000648:ultrastructure*