What makes Greta oto Butterfly Glasswinged
Found abundantly in Mexico and Panama, the Glasswinged butterfly aka Greta oto has a unique characteristics of having transparent wings. Its Spanish name is “espejitos”, which means “little mirrors” however scientists have confirmed its wings to be transparent/glass instead of mirrors. The sole purpose of these wings is to serve as camouflage against predators.
About 80% of the wing area is translucent while the rest 20% comprises of dark brown opaque borders. To be transparent, the tissues in the wings must neither absorb nor scatter light but let it pass through them with a homogenous refractive index. Following the principle of glass, the wings of Greta oto are covered with submicroscopic protrusions, which do not scatter light. The index of refraction is gradually changed over the protrusions from index of air to index of the material within the wing. In easy terms, the tissues present on the wings of Greta oto let the light pass through them without distorting its path, which makes them look transparent. [Source]