Masquerading moth deploys unique optical tricks to evade predators

Researchers from Murdoch University and The University of Western Australian found the forewings of the fruit-sucking moth (Eudocima aurantia) have the appearance of a crumpled leaf – but are in fact flat.

Dr Annie Jessop and Professor Gerd Schröder-Turk, from Murdoch’s School of Mathematics, Statistics, Chemistry and Physics, and lead researcher Dr Jennifer Kelley, from UWA’s School of Biological Sciences, published their research (with colleagues from the University of Salzburg, Austria) in Current Biology today.

They found the moth mimics the 3D shape and coloration of a leaf using specialised nanostructures on its wings.

“These nanostructures create a shiny wing surface that mimics the highlights found on a smooth, curved leaf surface,” Dr Jessop said.

“Structural and pigmentary coloration produces a leaf-like brown colour, with the moth exploiting thin-film reflectors to produce directional reflections – producing the illusion of a 3D leaf shape.”

The fruit-sucking moth is native to north Queensland and south-eastern Asia. The researchers made their discovery while visiting the London Natural History Museum, which holds one of the world’s largest collections of this group of moths.

“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,” Dr Kelley said.

“This suggests that moths are exploiting the way predators perceive 3D shapes to improve their camouflage, which is very impressive.”

Dr Kelley said there were many examples of animals and insects masquerading as uninteresting objects – from fish that resemble leaves to butterfly pupae that look like bird droppings.

“What is remarkable about this moth, however, is that it is creating the appearance of a three-dimensional object despite being almost completely flat,” she said. “This is the novel find to our study.

“This mimicry likely serves as a camouflage strategy, fooling predators into misidentifying the moth as an inedible object.”

The discovery follows the scientists’ previous research, which discovered a moth from the same group with shape-shifting patterns on its wings.