The glass-like quality of a White-spotted Clearwing (Greta annette) becomes revealed against the dappled light of the cloud forest understory. Although a great variety of marine organisms utilize transparency as a functional means of underwater invisibility, this type of optical camouflage is rare among terrestrial species for several reasons. Animals not living in water must protect their internal organs from damaging UV light and also possess rigid structural support for their bodies because they live in a non-buoyant medium; both of these are accomplished by pigments and opaque structures. In addition, the refractive index between living tissues and air means that reflections of light are a potential problem. Clearwing butterflies overcome this last hindrance by having the transparent portions of their wings covered with randomly-sized microscopic “nanopillars” – this results in their wings being remarkably unreflective from nearly all angles. Researchers studying this propose that these butterfly wings could be applied as a model to increase the efficiency of solar cells and in the manufacture of other non-reflective surfaces. El Triunfo Biosphere Reserve, Chiapas, Mexico.