Eyes Are Anti-Reflective

an elephant hawk-moth photographed head on with its bring pink lower body and yellow top, long legs and big yellow eyes

Biological Strategy

Moths

AskNature Team

Image: Derek Parker / Flickr / CC BY NC ND - Creative Commons Attribution + Noncommercial + NoDerivatives

Modify Light/Color

Color in living systems comes from pigments and the interaction of light with surfaces. Color serves many purposes for living systems, such as attracting prey or mates, providing warnings, or protecting through camouflage. To create the effects needed for each purpose, living systems must control the expression or visibility of pigments and the interactions (such as reflectance and refraction) of light. To do so, they have strategies that modify color or light to increase or decrease the color’s position, intensity, opacity, and more. Male hummingbirds, for example, have brightly colored feather patches on their throats; the coloring comes from pigments, structures that refract light, or a combination of the two. When a male hummingbird hovers near a potential mate, it modifies the angle of these feathers to create a bright, colorful display. However, when it needs to mute the colors to reduce conspicuousness, such as to avoid a predator, it modifies the angle again.

Search this Function

Protect From Animals

Animals–organisms that range from microscopic to larger than a bus–embody a wide variety of harms to living systems, including other animals. They threaten through predation, herbivory, defense, and parasitism, and they compete for resources such as water, nutrients, and space. Any given living organism commonly faces threats from a variety of animals, requiring strategies that effectively defend from each. Trout and other bony fish, for example, escape predators by having scales made of very thin, flake-like pieces of bone covered with slippery mucus. They also have behavioral strategies such as camouflage, fast swimming, and twisting and turning to achieve release from a predator’s grip.

Search this Function

Insects

Class Insecta (“an insect”): Flies, ants, beetles, cockroaches, fleas, dragonflies

Insects are the most abundant arthropods—they make up 90% of the animals in the phylum. They’re found everywhere on earth except the deep ocean, and scientists estimate there are millions of insects not yet described. Most live on land, but many live in freshwater or saltwater marshes for part of their life cycles. Insects have three distinct body sections: a head, which has specialized mouthparts, a thorax, which has jointed legs, and an abdomen. They have well-developed nervous and sensory systems, and are the only invertebrate that can fly, thanks to their lightweight exoskeletons and small size.

Search this Living System

Eyes of nocturnal moths are anti-reflective due to nanoscale protrusions.

Moths have unique sub-wavelength structures coating their eyes which dramatically minimize light reflection over a much broader range of wavelengths than conventional anti-reflective coatings. The outer surfaces of moth corneal lenses are covered with a regular pattern of conical protuberances, generally 200-300 nm in height and spacing. These protuberances reduce light reflection by creating a refractive index gradient between the air-lens interface, more gradually transitioning the change in light speed between the air and eye. These unique structures maximize light capture for seeing in the dark. Moth-eye inspired antireflective coatings that demonstrate high-performance over large band widths at low fabrication cost have recently been developed for solar panels, with many other potential products applications.

Image: Alan Jaras /

Image: Massel tow /

Image: Nigel Jones /

Related Innovations

Innovation: Academia

Scalable Anti-Reflective Film Inspired by Moths

Tokyo University of Science

Nano-film from Tokyo University of Science uses a thin layer of glassy carbon to reduce reflection and adhesion.

Innovation: Industry

Functional Surface Finishing Inspired by Plants and Insects

Fusion Bionic

Fusion Bionic uses laser interference patterns to efficiently produce micro and nano textures on a wide variety of materials.

Innovation: Academia

Anti-Reflective Nano-Coating Inspired by Fly Eyes

University of Geneva

Nano-coating from the University of Geneva creates nanoscale surface bumps that help to reduce reflection and adhesion.

Innovation: Industry

Camera for Capturing Polarized Light in Deep Space Inspired by Moth Eyes

NASA

HAWC+ from NASA is a telescope camera with small protuberances on the surface that increase light capture.

Last Updated October 18, 2016

References

We find differences in the shape of nipples between nocturnal and diurnal species, and that anti-glow reflectance levels are different at different wave-lengths, a result thereby contradicting the currently accepted theory of eye glow for predator avoidance. We find that there is reduced reflectance, and hence greater photon absorption, at UV light, which is probably a reason why moths are attracted to UV.

Journal article

Optical Modelling and Phylogenetic Analysis Provide Clues to the Likely Function of Corneal Nipple Arrays in Butterflies and Moths

Insects | August 22, 2019 | Adrian Spalding, Katie Shanks, Jon Bennie, Ursula Potter, Richard Ffrench-Constant

embedly preview

Reference

Journal article

Light on the moth-eye corneal nipple array of butterflies

Proceedings of the Royal Society B | December 6, 2005 | D.G Stavenga, S Foletti, G Palasantzas and K Arikawa

embedly preview

Reference

“The eyes of moths have two characteristic optical structures that probably function to increase the light sensitivity: the tapetal mirror and the corneal nipple array (Miller, 1979). The tapetum is composed of tracheoles at the proximal portion of the rhabdom and reflects unabsorbed light back into the rhabdom, thus providing a second chance for light to be absorbed. The corneal nipple array, known as the ‘moth-eye’ structure, is a set of protuberances of height about 200•nm, acting as a thin-film antireflection coating. These structures are basically retained in the apposition eyes of true butterflies, but all species in the family Papilionidae lack both (Bernhard et al., 1970; Stavenga et al., 2006).” (Takemura et al. 2007)

Journal article

Absence of eye shine and tapetum in the heterogeneous eye of Anthocharis butterflies (Pieridae)

Journal of Experimental Biology | 17/08/2007 | S.-y. Takemura, D. G. Stavenga, K. Arikawa

embedly preview

Reference

Other Biological Strategies

Biological Strategy

Fruit Skin Has Bright Blue Pointillist Appearance

Marble berry

The skin of the marble berry has a bright blue pointillist appearance due to distinct reflection of color on layers of cellulose microfibrils.

Desert locusts shift from a camouflaging color when solitary to a contrasting pattern that makes them stand out when swarming.

Biological Strategy

Social Changes Change Behavior and Appearance, Too

Desert locust

Swarming locusts eat toxic plants and change color as a warning to predators.

close up a green pine tree with purple tones on the branches in the sunlight

Biological Strategy

Fluorophores Enhance Photosynthesis

The cuticular wax of the dwarf mountain pine enhances photosynthesis by using fluorophores that convert UV light into blue light that can be used for photosynthesis, even under low-light conditions.

Piping plover walking on the beach towards the viewer

Biological Strategy

Birds Feign Injury to Draw Away Predators

Plovers

Plovers fake having a broken wing in order to lead predators away from their nest and protect their young.

cherry leaf roller caterpillar rolling a leaf

Biological Strategy

Caterpillars Reshape Leaves With Silk

Cherry leaf roller

Caterpillars use stitches made with contracting silk threads to roll leaves into a tube-shaped shelter

Biological Strategy

What Lights a Firefly’s Fire?

Common eastern firefly

The common eastern firefly produces light through a chemical reaction that energizes a molecule so it can release a photon.