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How to determine the true color of ancient insects and animals

An international team of researchers have successfully modeled the coloring of 200-million-year-old insect fossils trapped in amber. As a result, it may now be possible to know the colors of ancient insects of which only fossils remain.

The study was conducted by researchers from the Nanjing Institute of Geology and Palaeontology (NIGP) of the Chinese Academy of Sciences, along with colleagues in Germany, China, and the UK, and was published in the journal Science Advances.

Determining the color of Trichoptera fossils trapped in Burmese amber that date back to the mid-Cretaceous period might seem like an impossible feat.

However, the researchers knew that the specimens’ scales were structurally colored rather than the result of pigmentation.

Structural colors are common among butterflies and moths in the Lepidoptera order, and species in this order have some of the most diverse structural coloring produced by any insect.

As opposed to colors produced with pigmentation, structural coloring results from light interacting with skin, scales, or surface of a plant or animal. As the light hits the surface, complex structures within the cells produces different, vibrant colors.

Structural colors provide a number of functions including camouflage, warning predators and attracting potential mates.

Science has long been fascinated with structural coloring, but the history and evolution of structural coloring among lepidopterans has not been thoroughly investigated and is poorly understood.

The researchers examined the structural scale architecture of fossilized Jurassic Lepidoptera.

Different types of microscopes were used on the fossils in order to better understand the framework and morphology of the scales.

Jurassic lepidopterans have a bilayer scale where the upper layer consists of large fused cover scales and the lower layer has small fused ground scales. It’s a similar structure to some living moths today known as Micropterigidae.

The symmetrical and repetitive structure within the cells allows light to scatter and creates the structural coloring.

In this case, the researchers used optical modeling to show that the Jurassic Lepidoptera’s coloring would have taken on metallic hues.

The study also provided insight into the early evolution of lepidopteran scales.

It now may be possible to model the structural coloring of other lepidopterans in future studies as researchers work to learn more about these complex evolutionary processes within butterflies and moths.

By Kay Vandette, Staff Writer

Image Credit: YANG Dinghua

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