If you’re walking along in the rainforest, you might see straight through this stunning creature, and that’s exactly what the glasswing butterfly intends for you to do. This brush-footed butterfly that is native to Central and South America has the most attractive feature, which is its transparent wings, which resemble a clear window.
Naturally, these transparent wings confer a huge advantage to this butterfly due to its incredible ability to disappear into the background while flying or feeding on flowers.
Many butterflies found in the tropical rainforests across Latin America, from Chile to Mexico, have a wide range of strategies to avoid predators. Some butterflies have brownish and gray markings to be able to blend in with tree barks. Others like the famous Monarch butterfly (Danaus plexippus) have bright, splashy colors or striking patterns that suggest potential toxicity to predators. However, the glasswing butterfly is unique in its own way. “There aren’t a lot of things that are just trying to be invisible like the glasswings,” UC Berkeley researcher Aaron Pomerantz told KQED.
But how do these exotic species pull off the trick to fade from their hungry predators’ sight despite having clear wings?
While glasswing butterflies (Greta to) do have a splash cutting across orange and black, their main defense lies in their transparency.
Even as caterpillars, glasswings are mostly transparent, which is due to a lack of pigmentation. A video from KQED states that you can see through parts of its exoskeleton, offering a glimpse into their recent meal. Additionally, the exoskeleton is made of a thick material called chitin.
The caterpillar then emerges from the chrysalis after a week, and adult glasswing butterflies get their signature transparent wings due to a lack of pigmentation and some very special scales, which when seen up close resemble microscopic hair.
The function of the scales that are present on the transparent section of the wing is to allow these butterflies to have a strong, rigid wing that is also resistant to water.
In the specific case of the glasswing, its lack of pigment and hair-like scales allow light to pass through without getting reflected. However, these windows to the world wouldn’t safely serve their function if they were shiny.
This is where an even more unique adaptation comes into play, known as nanopillars. The surface of the glasswing butterflies’ wings are covered with them, and these tiny towers are composed of wax. “These structures are so small that they’re smaller than a wavelength of light,” Pomerantz said. “They’re just really, really, really tiny.”
The rough texture of these countless little nano-towers means that light isn’t reflected back the way it would be on a completely smooth surface. It’s these nanopillars that have given scientists like Pomerantz hope for new anti-glare technologies.
Underscoring the usefulness of this technology, Pomerantz said, “I think everyone can relate to light bouncing off their glasses or their phone screens and things like that.” For his part, he believes that further research into the glasswing’s nanopillars could increase the efficiency of solar panels, a vital energy source of the future.
“We’re interested in bioinspiration—things that we’ve learned from nature, and applying it to our technologies and our products,” he says. When you’ve seen the glasswing butterfly up close and personal as he has, it’s not hard to see why he’s so inspired.
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