200-million-year-old insect’s ‘true’ color revealed by fossils

Scientists from China, Germany and the UK have new evidence to reveal the "true color" of fossil insects, which are 200 million years old.

Structural colors have evolved in a myriad of animals and plants and result from the wavelength-selective scattering of incident light. These colors could be more vibrant and visually appealing than those produced via pigmentation. The colour plays an important role in intraspecific sexual signaling, aposematism and crypsis.

Recently, researchers from the Nanjing Institute of Geology and Palaeontology (NIGP) of the Chinese Academy of Sciences and their 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.

Using several ultrastructural parameters identified in Jurassic specimens, they 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.

The Jurassic lepidopterans exhibit a type 1 bilayer scale vestiture: an upper layer of large fused cover scales and a lower layer of small fused ground scales, besides herringbone ornamentation on the cover scale surface.

These colours 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.

Prof. WANG Bo from NIGP, and the team lead, said the widespread occurrence of wing scales in Jurassic lepidopterans and in tarachopterans strongly suggests that wing scales were widespread in stem Amphiesmenoptera prior to their apogee in the Lepidoptera.

Future studies will focus on optical response of scale nanostructures in other fossil specimens to understand models of the evolution of structural colors in lepidopterans, said the researchers.

The research was recently published in Science Advances.