![]() They tested the birds’ willingness to attack glossy and iridescent prey by presenting them with both iridescent and non-iridescent wing cases (with the same overall range of colours) as well as glossy and matte versions of the two. The team studied this by presenting real and artificial jewel beetle wing cases (the hardened forewings, called elytron, which cover the functional wings) to 32 chicks of the domestic fowl, Gallus gallus domesticus, that had never seen this kind of prey before. Credit: Dr Karin Kjernsmo Beetle beauty reducing the probability of attack “One of the challenges when studying the functions of such highly reflective structural colouration has been to separate the effects of the changeability of colours, the hallmark of iridescence, from the effects of simply having multiple colours at the same time, and also to separate the effects of gloss from the effects of iridescence,” says lead author Dr Karin Kjernsmo, from the University of Bristol’s School of Biological Sciences. Previously, they’d discovered that that iridescence can act as a highly efficient form of camouflage in the jewel beetle ( Sternocera aequisignata), but whether it could also protect prey after being detected was unknown. ![]() This striking feature has evolved independently in a wide range of organisms, from birds like the magpie and starling, to many insects including rose chafers, rosemary beetles and in the demoiselle.Ī team of researchers from Bristol University’s CamoLab in the UK have investigated why this metallic colouration has evolved so many times in the animal kingdom and what makes it such a successful anti-predator strategy. In iridescence, the hue and intensity of colours varies depending on the angle at which it is viewed. Another famous form of structural colouration is the vibrant blue of the brilliant South American blue morpho butterflies ( Morpho peleides). Iridescence is a form of structural colouration – meaning that the colours come from micro or nanostructures in the material, as opposed to pigments. ![]() They found that iridescence may confer a survival benefit by inducing hesitation or even an aversion response in attacking birds, and that the changing colours, a key feature of iridescence, is the characteristic important for this effect. For the first time, biologists have shown that the brilliant iridescence and gloss found in jewel beetles protects them by working as a deceptive warning colouration after being detected by avian predators, according to a recent study in the journal Animal Behaviour.
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