How Butterflies Can Induce Transparent Wings

Most people, when they think of butterflies, imagine big colorful wings. So it was much to scientists' surprise when they found a species of Central American butterflies that have transparent wings. This species is knowns as the Glasswing butterfly (Greta oto). The big research question is "how do butterflies accomplish transparency"?

Researchers, after analyzing the wings under the microscope, identified an abundance of antireflective scales on the wings' outer membrane. Using confocal imaging, scientists, additionally, discovered that the opaque, colored areas of the wings were made up of tightly organized, oval scales whereas the translucent areas wings had widely spaced out fibrous scales. In addition to the opaque and translucent scales, there were water-resistant scales scattered along the entire wing membrane. This was anticipated because butterfly wings need water-resistance scales so their wings don't stick together, from cohesive forces.

To the researchers' surprise, only 2% of all scales were antireflective and translucent and 95% of the scales were opaque.

What scientists also conclude contributes to butterfly's camouflage is the wing's wax bumps. These bumps allow more light to travel through the wing which furthermore contributes to the wing's overall optical illusion and reduced glare. In a separate test scientists analyzed how wax bumps influence light reflection. In their control group, they found that Glasswing Butterflys' wings reflect only 2% of light traveling through the air. In their treated groups they removed the waxy wing bumps from the butterflys' wings. In the absence of waxy bumps, the butterflies' wings reflected 3 times as much light.

Scientists so far, know that translucent scales and wax bumps on the wings contribute to the Glasswing butterfly's camouflage. However, given that translucent scales only comprise 2% of all scales, scientists hypothesize that there are other biological factors of the wing that aid in the wing's translucency.

Achieving Transparency is no easy feat for any organism. The species must minimize any scattering of light. Hence, translucency is a marvel of science and evolution that greatly astounds scientists to this day. Moreover, the better we understand translucence in other species, like the glass wing butterfly, the better we can attempt to implement antireflective technologies into modern technology and consumer goods.

Sources:

A.F. Pomerantz et al. Developmental, cellular and biochemical basis of transparency in clearwing butterflies. Journal of Experimental Biology. Vol. 224, May 2021. doi: 10.1242/jeb.237917.