Transparent, Antireflective, Cryptic

Cicada in the genus Neotibicen

Some species of cicadas can be difficult to locate even when loudly calling from trees. Their wings are transparent. Visually, they appear like part of the background because we can see the background through the wings. Blending into the background with transparent structures only works if the surface is non reflective. In the photo of the cicada (left) you can see the reflection of the sunlight off the the cuticle of the cicada’s body. If you look closely, you will note that the wing is not reflective at all.

The anti-reflective properties of cicada wings are due to nano scale structures that arise from the wing like cones. Arrays of cones over 200 nm in height have very low reflectance. A group of scientists* used Atomic Force Microscopy (AFM) to lower the height of the nano cones on a cicada wing to about 25 nm. The more of the structure that was removed by AFM (lower height) the more reflective the wing surface became.  A reflective wing would make the cicada stand out from the background and not be good for camouflage.

*Gregory S. Watson, Sverre Myhra, Bronwen W. Cribb and Jolanta A. Watson. Putative Functions and Functional Efficiency of Ordered Cuticular Nanoarrays on Insect Wings