Greta Oto – The Glasswing Butterfly

Have you ever wished to be invisible?

To fade into the background, unnoticed. For the glasswing butterflies of the tropical forests in South and Central America, invisibility is a matter of survival. Surrounded by hungry predators, they must find ways to disappear. Some butterflies rely on mysterious camouflage, blending seamlessly with their surroundings.

Others use aposematism—bright colors and bold patterns that warn predators of their toxicity.

Greta Oto does carry some warning marks: a bright white stripe against a black background, with orange to red outlines along its wings. Yet this is not its main defense. Its transparent wings allow it to vanish from sight when in flight.

Caterpillar Transparency

Even the caterpillars of the glasswing butterfly use transparency as camouflage. Parts of their exoskeleton are see‑through, offering a window to their latest leafy meal. This exoskeleton is made of chitin, a material both strong and flexible. In most insects, chitin is mixed with pigments that give it color. But in the glasswing caterpillar, some areas lack pigment entirely.

Metamorphosis

When the caterpillar stage ends, the insect attaches itself beneath a leaf or stem, forming a chrysalis. Inside, it undergoes metamorphosis. About a week later, the transformation is complete. The adult butterfly emerges, unfolding its delicate new wings for the very first time.

The Science of Transparency

In the laboratory of Nipam Patel at the University of California, Berkeley, researcher Aaron Pomerantz studies how Greta Oto forms its transparent wings. They are made of the same clear chitin from its caterpillar stage, but here the chitin is stretched—astonishingly thin and rigid.

Most butterflies’ wings are covered with colorful overlapping scales. Greta Oto also has scales along the wing edges, but they look more like tiny hairs. Thin and spread apart, they allow light to pass freely.

Nature’s Anti‑Glare Design

Clear wings alone would not help the butterfly hide if they were shiny. Under magnification, the wing surface between the hairs appears rough, covered with microscopic towers made of wax. These are called nanopillars. If the surface were smooth, light would bounce off it. Nanopillars act as nature’s original anti‑reflective coating.

Researchers found that when chemicals were used to remove the nanopillars, the wings reflected more light. While many butterflies shimmer in sunlight, Greta Oto reflects almost none. What makes the glasswing butterfly special is not its brilliance, but its ability to fade away.