Reflected and refracted light creates the many bright and shining colours of these insects. This dazzling natural display is created by a combination of embedded pigments and sculpted surfaces on each insect’s external skeleton.
Different pigment chemicals are responsible for different colours. Carotenoids produce yellow, orange and red hues, while bilins may be green, or blue if linked with proteins. They reflect and absorb different wavelengths of light, and the wavelengths that are reflected are the ones that we see as colour. Typically humans can see wavelengths of 390–700 nanometres, with lower wavelengths perceived as blue, and higher ones as red.
Many insects also have multiple thin layers over their upper surfaces to help protect them and prevent dehydration. Variations in thickness and chemical composition of these layers can interfere with the transmission of light, refracting and scattering it back.
The shape of the surface layer can reflect light in a multitude of directions, with micro-folds, grooves, pits, hairs and scales all helping to produce complex colours and effects.
The formation and purpose of these colours is scientifically interesting, with research having applications in areas such as nanotechnology. But these insects are also simply beautiful examples of the spectacular diversity of the natural world.
Urania, a genus of moths in the family Uraniidae.
Morpho butterflies are well known for their vibrant blue colouration. They also reflect a lot of light in the ultraviolet portion of the spectrum. A technique called nano-fabrication takes inspiration from Morpho wing scales for the development of new display technologies that may eventually replace liquid crystal display screens.
Males of some species of orchid bee use their bright colours coupled with scented oils collected from orchids to attract females. Gathering together in sunlit spots in the forest, they fly in and out of the light to create a dazzling display of flickering colours.
Created in the late 18th century by William Jones, Jones’ Icones is one of the most beautiful and scientifically important early works on butterfly and moth collections found in Britain. To illustrate the iridescent colours of some species, gold leaf was added to the watercolour illustrations.