Intraspeciifc Structural Color Variation In Flower Beetles

In the biological world, coloration has two major sources: pigments andphotonic structures. The pigmentary coloration is also known as chemicalcoloration and the structural coloration is physical coloration due to the origin ofphotonic structures. In principle, structural coloration results from theinteractions of light with featured microstructures comparable to visiblewavelength by interference, diffraction, scattering. Compared with pigmentarycoloration, structural coloration takes advantages such as non-fading andenvironmental friendliness, leading to potential applications in various fieldssuch as display, decoration, and anti-counterfeiting. The studies on themechanisms of structural coloration in nature may inspire not only tailoring ofnovel artificial structures but also the way of their engineering. In this thesis, wemainly study the intraspecific structural coloration variation origin of flowerbeetles Torynorrhina lfammea. In addition, we study the structural coloration inthe elytra of flower beetles Ischiopsopha bifasciata.This thesis consists of four chapters. In the first chapter, we introduce twokinds kinds of coloration mechanism of creatures in nature with emphasis on theorigins of structural coloration and the intraspecific variation coloration.In the second chapter, we introduce the experimental techniques andtheoretical approaches on the study of structural coloration. In the third chapter, we study the intraspeciifc structural coloration variationorigin of lfower beetles T. lfammea. The microstructure and spectral propertiesare obtained by spectral measurements and electron microscopy. It is found thatthe elytra have three-dimensional photonic crystal microstructure composed ofmultilayer and two-dimensional amorphous diffraction grating. The elytra showinteresting optical features，e.g. negative diffraction and backscattering. Withtransfer matrix methods, the simulation results reveal the diffraction originatesfrom the anticrossing behavior of multilayer bands and grating bands. Bymanipulating the period of multilayer, the coloration of beetles T. lfammea iseasily controlled, which is a much more efficient v^ay than that of gratingconstant tuning. The unraveled mechanism could be advantageous for thepotential exploration of novel dispersive optical elements.In the fourthterth, chap, we study e structural coloration in the elytra offlower beetles I. bifasciata. There are two layers of microstructure:three-dimensional photonic crystal structure and curved multilayer structure, wepoint out that the curved multilayer structure enables not only normal but alsooblique incidence, thus larger solid angle of incidence. By spectral measurements,we ifnd that both emergence angles and wavelength are broadened. Thecoloration strategy of flower beetles L bifasciata may benefit the interspecificcommunications.