Structural Color in Amber-Entombed Wasp: A Detailed Study Using NS-FDTD Simulations

The multilayer reflectors of insect epidermis can produce unique structural color through interactions with light. Many fossilized insects, like amber-entombed wasps, present structural colors. However, how this multilayer structure and structural colors are preserved during the fossilization process is still being determined. We use a transfer matrix method (TMM) and a Non-Standard Finite Difference Time Domain (NS-FDTD) simulations to analyze the effects of both expected compressions and expansions of the epidermis layer thickness during fossilization on its structural colors. We estimate the variations of epidermis layer thickness due to the fossilization by measuring their color distances. Surprisingly, we find that the structural coloration of the multilayer reflectors, ranging from blue to green, emitted by many insects remained unchanged from about +5% expansion to -12% compression of their thickness. These findings suggest that, first, insects might have kept their original colors during the fossilization process. Second, the appearance of these structural colors in insects might not just be by chance, but could also be a result of specific evolutionary choices.