Layers Create Multihued Appearance

colorful and metallic beetle on a light purple flower

Biological Strategy

Scarab beetles

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Image: Daniel Norin / Unsplash / Free non-commercial use

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.

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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.

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Carapace of beetle appears multihued because of ultrathin layers in a corkscrew orientation.

Image: Udo Schmidt /

“Gymnopleurus virens beetles have shells that change from red in the centre to green around the edges or from green to blue…the shells are made of thousands of ultrathin layers, with each successive layer slightly twisted in relation to the one above. ‘It’s a corkscrew effect,’ says Brink.

“This corkscrew structure causes the shell to reflect only that portion of light which has the same corkscrew orientation – known as circularly polarised light. ‘When the corkscrews match, you get astonishingly efficient reflection of almost 100 per cent,’ says Brink.

“The team also found that the shells have defects, in which a layer swings around by 90 degrees. This in turn changes the spacing between the layers, allowing the shell to reflect more than one wavelength of light. These defects combine with the shell’s shape to give it its iridescence.” (New Scientist 2007:17)

Beetle’s beauty lies in imperfection. New Scientist, 4/7/2007, Vol. 194 Issue 2598, p17-17, 1/4p; (AN 27198858)

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