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Beetles & other insects
It is structural color that is responsible for the beautiful shimmering blue of neotropical Morpho butterflies and the glistening green of many tropical beetles. Another interesting group of insects, the day-flying uranid moths, get their shiny green color from a somewhat different scale design. Their scales use a combination of ridges and air pockets to produce iridescence.
The colors of many beetles are also produced by the structure of their body surface. The epicuticle, or outermost surface, of iridescent beetles is made of many stacks of slanting, platelike layers, which are oriented in different directions. These layers bend and then reflect the incoming light the same way that the ridges of iridescent butterfly and moth scales do and they, too, produce structural colors. Underneath the stacked refractive plates of these beetles and the ridges of many iridescent butterfly scales is a layer of pigment that enhances the effect of the iridescence.
Most insect structural colors are in the green-blue-violet range, but red, gold and copper colors may also be produced in this way. Structural color and its intensity are determined by several factors, including the thickness and spacing of the layers of the scales or epicuticle, the number of these layers, and the angle of the incoming light.
Why is it that many tropical beetles are iridescent? Unlike birds, most insects do not use showy color to attract mates: they rely primarily on chemical attraction for this. It might seem that the colorful appearance of these beetles would actually be detrimental because it would tend to advertise their presence to predators. In fact, these creatures are surprisingly well camouflaged. Their leafy environment is often illuminated by intermittent flashes of sunlight at breezes move through the trees above them. The glistening surfaces of these beetles actually blend in well with their surroundings.