Scientists at the Natural History Museum have identified the process used by tiny structures within butterfly wing scales that allows them to shimmer
By studying a butterfly from New Guinea – Lamprolenis nitida – zoologists at the Natural History Museum have discovered how two similarly sized microscopic structures within a single wing scale are responsible for the butterfly’s changing colour and shimmering wings. The butterfly appears matt brown when lit from above but bright green to red when lit from the front and blue to violet when lit from the back.
Dr Abigail Ingram, a zoologist at the Museum, said ‘Butterflies are some of the most brightly coloured insects we know to exist. We’ve found for the first time that more than one structure causes the colour changes in butterflies. Because this sort of iridescence is seen elsewhere in the animal world, our discovery could affect other iridescent plants and animals, too. Since all of the interference colours observed from the L. nitida hindwing do not occur in the order in which we would expect, we surmised that two similarly sized structures were responsible.’
L. nitida lives in the forests of New Guinea, which are also home to many other butterfly species, so it is essential for butterflies to recognise others of the same species. Light levels are very low in the forests, with shafts of light occasionally breaking through the overhead canopy. A bright directional light flash whenever a light shaft is encountered makes the butterflies very noticeable. Only the males of this butterfly employ the colour changing ability and Dr Ingram and her colleagues concluded that it is probably important during competitive encounters between males – the iridescent male wing colours are probably used in threat displays.
Dr Ingram commented ‘L. nitida uses two microstructures in a single wing scale. Each one causes a separate iridescent signal and different colours can be seen in different directions. We’ve never seen this in another butterfly, animal or plant. This discovery is therefore new to the field of butterfly structural colour, but also more generally to the study of structural colours in nature.’
Butterflies display some of the most vivid colours in nature and they are a rich source of inspiration for engineers developing innovative new materials. The colours are the result of light striking the surface of the wing scales, causing iridescence or structural colour. Recently, there has been renewed interest in the nanostructure of butterfly scales because their optical properties have potential applications to technology. This new discovery, together with previous research that revealed we can not only make the iridescent structures found in nature with conventional engineering, but we can also culture cells to make them for us, could be applied in the field of biomimetics.
• Dual gratings interspersed on a single butterfly scale is published in Journal of The Royal
• biomimetics is the extraction of good design from nature using the methods and systems found in nature and applying it to the study and design of engineering systems and modern technology
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