Data from: Structural colours in diverse Mesozoic insects

Structural colours, nature’s most pure and intense colours, originate when
light is scattered via nanoscale modulations of the refractive index.
Original colours in fossils illuminate the ecological interactions among
extinct organisms and functional evolution of colours. Here we report
multiple examples of vivid metallic colours in diverse insects from
mid-Cretaceous amber. Scanning and transmission electron microscopy
revealed a smooth outer surface and five alternating electron-dense and
electron-lucent layers in the epicuticle of a fossil wasp, suggesting that
multilayer reflectors, the most common biophotonic nanostructure in
animals and even plants, are responsible for the exceptional preservation
of colour in amber fossils. Based on theoretical modeling of the
reflectance spectra, a reflective peak of wavelength of 514 nm was
calculated, corresponding to the bluish green colour observed under white
light. The green to blue structural colours in fossil wasps, beetles, and
a fly most likely functioned as camouflage, although other functions such
as thermoregulation cannot be ruled out. This discovery not only provides
critical evidence of evolution of structural colours in arthropods, but
also sheds light on the preservation potential of nanostructures of
ancient animals through geological time.