The fruit-sucking moth (Eudocima aurantia) in its resting position, showing its leaf-mimicking wing. [Image: Bridgette Gower Aussie Macro Photos]
In an animal kingdom defined by predator–prey relationships, many species have evolved protective mechanisms, such as hard shells, sharp thorns and camouflage. Typically, camouflage is associated with avoiding detection—like a butterfly blending into the bark of a tree. But some organisms rely on resembling other predators, inedible objects or even bird droppings, as is the case with some butterfly pupae.
New work looks at a leaf-mimicking nocturnal moth and the remarkable way that it mimics a leaf—not only in coloration but in appearance of shape as well (Curr. Biol., doi: 10.1016/j.cub.2025.01.029). The flat wing of the moth features surface highlights from nanostructures that make it look like it has the 3D midrip (the large vein down the center of a leaf), veins and the curvature of a crumpled leaf.
A remarkable moth
A research team from two Australian universities, Murdoch University and the University of Western Australia, noticed the leaf-like critter while visiting the London Natural History Museum, UK, which has one of the largest collections of this insect group. The moth is a fruit-sucking species called Eudocima aurantia that is endemic to Southeast Asia and north Queensland, Australia.
While many organisms use mimicry to hide from predators, the researchers say this moth’s form of camouflage is particularly noteworthy. “What is remarkable about this moth, however, is that it is creating the appearance of a three-dimensional object despite being almost completely flat,” said study author Jennifer Kelley, University of Western Australia. “This is the novel find to our study.”
Kelley and her colleagues first studied the wing with X-ray tomography to confirm that the midrib, veins and curvatures were not structurally real. After the resulting tomogram showed that the wing was flat, they photographed specimens from overhead while altering the illumination angle to investigate the angle-dependent reflection properties of the wings. Then the team used stereo microscopy to take a closer look at the scales and observed that they were all oriented in the same direction. This means that angle-dependent changes from reflection were caused by differences in scale shape rather than orientation.
Evolved 3D camouflage
Specialized scales with morphology similar to that of a thin-film reflector combined with structural coloration undergo scattering and color mixing—creating a “shiny” brown appearance in the regions of the wing generating directional reflections.
The researchers found that the crumpled-leaf look of the moth is achieved with a combination of structural and pigmentary coloration. Specialized scales with morphology similar to that of a thin-film reflector combined with structural coloration undergo scattering and color mixing—creating a “shiny” brown appearance in the regions of the wing generating directional reflections. In contrast, the nonspecialized scales look brown because of their pigmentation.
The nanostructures responsible for reflecting light are only found on the parts of the wing surface that would be convex on a leaf, particularly around the perceived midrib and veins. According to the team, the directional reflections—which are visually associated with highlights on surfaces with varying topography—created by the mirror-like properties of the thin-film reflectors are indicative of an evolved “3D shape mimicry” adaption that is key to the moth’s ability to masquerade. Kelley and colleagues note that predators’ cognitive processes, or the way that they classify objects, played a role in the evolution of such camouflage strategies.
“It is intriguing that the nanostructures which produce shininess only occur on the parts of the wing that would be curved if the wing was a leaf,” Kelley said. “This suggests that moths are exploiting the way predators perceive 3D shapes to improve their camouflage, which is very impressive.”