Butterfly Wing Structure – Transparency Edition

May 28, 2016 • 7:48 PM UTC

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Aaron Pomerantz

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In the past I have posted about some of my experiences with the Foldscope in the Amazon rainforest, and more recently about investigating structural color in butterflies in the field (see here and here ). I even just realized that others have made posts contributing to a butterfly scale database!
For this particular trip to Ecuador, I was interested in species of butterflies and moths that display transparency in their wings.

At first you might say to yourself, well maybe these butterflies just lack scales within the transparent regions. However, taking a look with the Foldscope tells a different story…

Notice in this Haetera butterfly species that the transparent wing is in fact covered in scales. Looking at a different region (the colorful eyespot on the wing) reveals completely different scale morphology.

Here is a Cithaerias butterfly, commonly known as the Blushing Phantom. The scale structures in the transparent region appear different than the Haetera.

The above are particularly interesting, butterflies commonly known as Glasswings. The scales in the transparent regions appear a bit forked and the colorful scales (likely containing pigments) have a completely different morphology.
By looking at just a handful of transparent butterflies, already we can begin to hypothesize that nanostructure development that produces wing transparency could have evolved multiple times and perhaps butterflies can achieve transparency in completely different ways.
What are your thoughts? The physics behind nanostructures that allow for transparency is truly intriguing and I hope to delve into this further.