Psychedelic beetle shows physicists its true colours
Press Release
24 April 2007
Scientists have discovered that the bright lime green colour of a tropical beetle, native to South America comes from psychedelic swirls of red and yellow spots in its wings. The novel structure in the wings of the beetle is reported this month (April 2007) in the New Journal of Physics, jointly owned by the Institute of Physics and the German Physical Society. The structure could provide the blueprint for new vivid optical displays from neon signs to digital camera screens.
The green beetle, Plusiotis boucardi, uses a novel microscopic structure that looks like a honeycomb on the outer surface of its wings to control the colour and polarisation of light reflected from it rather than containing green pigment. The structure could be the basis for optical displays in the future that use metal-free micro-mirrors tuned to give out specific colours.
Lead author Dr Sharon Jewell at Exeter University said: “To the naked eye the beetle is plain green in colour, the shade of which varies slightly depending on the angle that you look at it. However, when we looked at it under the microscope at low magnification we saw a vivid hexagonal pattern of red and yellow dots on a green background. Such intense colours being produced from what at first glance appeared to be a rather plain and unremarkable green beetle was completely unexpected.”
By examining a cross-section of the wing the researchers could see how the actual structure of the beetle shell controlled the colour and polarisation of the light reflected. Each red and yellow spot seen under the microscope corresponded to the base of tiny bowl-shaped dimples on the surface of the beetle, just 10 microns across, that recessed into the shell itself.
Dr Jewell continued: “The shell consists of ultra-thin twisted fibrous layers, the pitch of which controls the polarisation and colour of the light reflected from it. This is the same as the way that the molecules in a twisted liquid crystal layer used in LCDs control the colour that is seen. The red and yellow spots produced combine with the green background to give the beetle its camouflaging colour.”