Scientists at the Natural History Museum have identified for the first time how the tiny structures that make butterfly wings shimmer, and seemingly change colour, actually work
'We've found for the first time that more than one structure within a single scale causes the colour changes in butterflies,' says Dr Abigail Ingram, butterfly expert (zoologist) at the Museum.
Butterflies display some of the most vivid colours in nature and these colours are the result of light striking structures on the surface of the wing scales. They are known as iridescence or structural colours.
The centre of the study was a butterfly from New Guinea called Lamprolenis nitida.
Butterfly wing under SEM (Scanning Electron Microscope)Butterfly wing under SEM (Scanning Electron Microscope)
This butterfly has an intriguing characteristic - it appears matt brown when lit from above but green to red when lit from the front, and blue to violet when lit from the back.
'L. nitida uses 2 nanostructures in a single wing scale, each of which causes a separate iridescent signal of different colours that can be seen in different directions,' says Ingram.
'We've never seen this in any other butterfly, nor indeed other animals or plants. This discovery is therefore new to the field of butterfly structural colour but also more generally, to the study of structural colours in nature.'
L. nitida> lives in the forests of New Guinea with thousands of other species of butterflies. They therefore need to be able to recognise each other.
Light levels are very low in these dense forests and occasionally a shaft of light breaks through the overhead canopy and will light up a butterfly and make it very noticeable.
Only the males butterflies of this species use the colour changing ability and Dr Ingram and her team say it is probably used in threat displays to warn off other males.
Understanding how these tiny nanostructures in the butterfly wings cause optical effects is important because scientists want to replicate these structures, and other good designs from nature and use them in modern technology.
This is known as biomimetics and already scientists have made iridescent structures using conventional engineering and Museum scientists have grown cells (culture cells) that produce the structures for us.