Structural colors have evolved in a myriad of animals and plants and result from the wavelength-selective scattering of incident light. Recently, researchers from NIGPAS and colleagues from Germany and the UK reported scale architectures from Jurassic Lepidoptera from the UK, Germany, Kazakhstan and China and Tarachoptera from mid-Cretaceous Burmese amber. Which means some ancient “true color” of fossil insects were revealed. The research was published in Science Advances on April 11, 2018.
Using the ultrastructural parameters identified in Jurassic specimens, the researchers demonstrated the use of optical modeling to describe the theoretical optical properties of the type-1 bilayer scale arrangement, thus providing the earliest evidence of structural colors in the insect fossil record. Optical modeling confirms that diffraction-related scattering mechanisms dominate the photonic properties of the fossil cover scales, which would have displayed broadband metallic hues as in numerous extant Micropterigidae.
The fossil tarachopteran scales exhibit a unique suite of characteristics, including small size, elongate-spatulate shape, ridged ornamentation and irregular arrangement, providing novel insight into the early evolution of lepidopteran scales. Combined, these new results provide the earliest evidence for structural coloration in fossil lepidopterans and support the hypothesis that fused wing scales and the type 1 bilayer covering are fundamental features of the group.
Given the presence of structural coloration in these basal fossil lepidopterans, the advent of major lepidopteran clades by the Cretaceous raises the possibility that this taxonomic radiation may have been accompanied by increased diversity in scale shape, microstructure and optical effects.
Reference: Zhang Qingqing, Mey W., Ansorge J., Starkey T.A., McDonald L.T., McNamara M.E., Jarzembowski E.A., Wichard W., Kelly R., Ren Xiaoying, Chen Jun, Zhang Haichun, Wang Bo* (2018) Fossil scales illuminate the early evolution of lepidopterans and structural colors, Science Advances 4: e1700988. doi:10.1126/sciadv.1700988.