Glasswing butterflies
How the glasswing 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, with predators like rats and birds struggling to keep track of glasswings as they flit between plants.
The reason behind the transparent wings sounds simple; they hardly reflect any light. 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, but the surface of the Greta oto’s wings are covered in randomly scattered pillars 50- to 100-times thinner than a human hair. These pillars are of different heights and widths, which, when combined with their chaotic distribution, work to redirect light through the wing tissue regardless of the angle the wing is hit from. A few rays bounce off, but this structure is so effective that it produces a surface less reflective than clear glass.
“Most light travels straight through the glasswing’s fine tissue”