Researchers from Ireland have analyzed the preserved scales from wing cases of two fossil weevils, which were from the Late Pleistocene era, around 13,000 years ago. They did it in order to better understand the origin of light-scattering nanostructures, which are present now in present-day insects.
They found the wing cases of the fossil weevils, which contained preserved photonic ‘diamonds,’ which is one of the many types of nanoscopic structure which usually interacts with light, in order to produce some of the purest colors in nature.
The coverings of many insects include repeating units, which are placed in a crystalline formation, which interacts with visible light, in order to produce structural colors. For most of these insects, the iridescent colors do a lot of things, from signaling potential mates to camouflage, to warning off predators. Up until now, the evolutionary history of these structures has not been defined clearly.
This study shows that the fossil record has excellent potential as a way to unearth the evolutionary history of structural colors in many insects.
They used powerful electron microscopes, together with state-of-the-art synchrotron X-ray scattering, in order to find and describe a rare 3D photonic crystal nanostructure from the fossil weevil scales. The green and blue colors are quite similar to those of the new weevils from the same genus.
3D nanostructures are very rare in the fossil record. This is the second time such nanostructures have been found.
Similar substrate-matching green colors have been taken care of for a very long time, the thing that suggests that, on the weevils, there were the same selective pressures for camouflage. The study indicates that the weevils’ colors evolved due to the camouflage on the background before they were able to signal potential mates, or warning off predators.