How the glasswing butterfly hides in plain sight and why it could stop people from going blind

In the tropical forests of Central and South America, and occasionally as far north as Texas, there’s a puzzling little butterfly called Greta oto – the glasswing butterfly. As its name would suggest, this species has a remarkable set of wings. They are largely transparent with coloured borders. Being almost see-through is an effective form of camouflage. Predators like rats and birds struggling to keep track of glasswings as they flit between plants.

The science behind the glass wing

The reason behind the transparent glasswing butterfly wings sounds simple; they hardly reflect any light. Instead, most light (from infrared to ultraviolet) travels straight through the fine tissue. The colours and patterns on other butterflies’ wings are created by the reflection and scattering of light. So what makes this species different? It all comes down to the nanostructure of the wings.

Nature usually favours order. However, the surface of the glasswing butterfly wings are covered in randomly scattered pillars 50- to 100-times thinner than a human hair. These pillars are of different heights and widths. This factor, combined with their chaotic distribution, work to redirect light through the wing tissue regardless of the angle the wing is hit from.

This structure is so effective that it produces a surface less reflective than clear glass.

This article was originally published in How it Works Issue 115, written by Victoria Williams

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