The Structure Of The Color And Structure Of The Beetle Color

Color produced in nature originates from either pigments called chemical color or microstructures called physical color.Structural color results from the interactions of natural light with featured microstructures comparable to visible wavelength.Over chemical color,structural color has several advantages such as higher saturation, non-fading if microstructures retain unchanged and environmental friendliness.Color change can be triggerred by changes in pigments or microstructures.Most of color change in nature is due to pigment changes.Research on structural color change has been less studied.Investigations on structural colors can not only reveal structural origins and steering strategies but also inspire our design and frabrication of artificial photonic structures.In the first Chapter,the background of color production and color vision of human, birds and beetles are briefly introduced.We also briefly review the recent progress of structural color studies.In the second Chapter,experimental setups and theoretical methods used for structural color studies are discussed.In the following three chapters,experimental and theoretical results on structural colors in Coleoptera are given.The first two are focused on structural colors and the third one on the structural color change.In the third Chapter,the inconspicuous structural coloration of the elytra of beetle chlorophila obscuripennis fairmaire is studied.It is found that the elytra are composed of hexagonal pits.Bluish green color perceived by naked eyes is actually a color mixing of green and cyan,which are located in the rim and basin of the pits, respectively.Both of the colors originate from elytral multilayer microstructures.The color difference is caused by the different periods in the different regions of the pits. We discover the inconspicuous coloration is due to the scatterings of the pits.The camouflage strategy may inspire artificial design used in stealth technology.In the fourth Chapter,the coloration strategy of beetle Heterorrhina sexmaculata sexmaculata is studied.Through 3D photonic crystal microstructures in the elytra, light will emerge in mirror reflection,backscattering and diffraction direction as well. In fact,the orange and green colors are produced by the summations of all scattered light in the range of some solid angles.The color difference comes from the different solid angle range.In the diffused light condition,color is not sensitive to the angle change.This kind of coloration may be of significance for specific recognition and communication.In the fifth Chapter,through the research on reversible color change in dry and wet state of longicorn beetle Temsisternus isabellae,for the first time,we find the color change of this beetle comes from 1D photonic crystal microstructures whose period can be altered by water.Hair on the elytra is found to be hydrophilic and in wet state the melanoprotein layer can absorb water and swell.This kind of color change is different from what we have known so far.