title: Cryptic iridescence in a fossil weevil generated by single diamond photonic crystals.
abstract: Nature's most spectacular colours originate in integumentary tissue architectures that scatter light via nanoscale modulations of the refractive index. The most intricate biophotonic nanostructures are three-dimensional crystals with opal, single diamond or single gyroid lattices. Despite intense interest in their optical and structural properties, the evolution of such nanostructures is poorly understood, due in part to a lack of data from the fossil record. Here, we report preservation of single diamond (Fd-3m) three-dimensional photonic crystals in scales of a 735,000 year old specimen of the brown Nearctic weevil Hypera diversipunctata from Gold Run, Canada, and in extant conspecifics. The preserved red to green structural colours exhibit near-field brilliancy yet are inconspicuous from afar; they most likely had cryptic functions in substrate matching. The discovery of pristine fossil examples indicates that the fossil record is likely to yield further data on the evolution of three-dimensional photonic nanostructures and their biological functions.
authors.affiliation: Department of Geology and Geophysics, Kline Geology Laboratory, Yale University, 210 Whitney Avenue, New Haven, CT 06520, USA UCD School of Geological Sciences, University College Dublin, Belfield, Dublin 4, Ireland maria.mcnamara@ucc.ie.
authors.forename: Maria E
authors.initials: ME
authors.lastname: McNamara
authors.affiliation: Edward Grey Institute, Department of Zoology, University of Oxford, Tinbergen Building, South Parks Road, Oxford OX1 3PS, UK vinodkumar.saranathan@aya.yale.edu.
authors.forename: Vinod
authors.initials: V
authors.lastname: Saranathan
authors.affiliation: Department of Geology and Geophysics, Kline Geology Laboratory, Yale University, 210 Whitney Avenue, New Haven, CT 06520, USA.
authors.forename: Emma R
authors.initials: ER
authors.lastname: Locatelli
authors.affiliation: Department of Nano and Electronic Physics, Kookmin University, 77 Jeong-neong Ro, Seongbuk-gu, Seoul, Korea Department of Applied Physics, Yale University, Becton Centre, 15 Prospect St., New Haven, CT 06520, USA.
authors.forename: Heeso
authors.initials: H
authors.lastname: Noh
authors.affiliation: Department of Geology and Geophysics, Kline Geology Laboratory, Yale University, 210 Whitney Avenue, New Haven, CT 06520, USA Yale Peabody Museum of Natural History, 170 Whitney Avenue, New Haven, CT 06520, USA.
authors.forename: Derek E G
authors.initials: DE
authors.lastname: Briggs
authors.affiliation: UCD School of Geological Sciences, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Orr
authors.affiliation: Department of Applied Physics, Yale University, Becton Centre, 15 Prospect St., New Haven, CT 06520, USA.
authors.forename: Hui
authors.initials: H
authors.lastname: Cao
mesh_terms: D005075:Biological Evolution; D002170:Canada; D018130:Diamond; D005580:Fossils; D010944:Plants
chemical_list: D018130:Diamond
keywords: Coleoptera; fossil colour; iridescence; photonic bandgap materials; photonic crystals; structural colour