Pointillistic Mixing of Interference Colours in Cryptic Tiger Beetles

摘要

Tiger beetles exhibit a novel mechanism for matching the reflectance spectrum of the body to that of its background. The cuticle is sculptured with hexagonally packed, deep its approx. 10 microns diameter, that are coated with an 18-layer interference filter. The reflectance spectrum has substantial global variation over a 50 micron patch of surface (e.g., a group of 9 bright green pits surrounded by magenta pits). Because these dimensions are well below the resolution limit of animal eyes, a predator sees a spectrum that is an average of the spatially inhomogeneous reflectance spectra, with peak intensity that is controlled by the depth of surface sculpturing. By varying layer thicknesses and sculpturing, different morphs of tiger beetle match the different soils on which they occur, such as wet brown sand, reddish Tertiary sands, or grey basalt pebbles. Keywords: Camouflage, Reprints. (aw)