Читать книгу Extreme Insects - Richard Jones - Страница 11

NAME	golden chafers in the genus Plusiotis
LOCATION	Central and South America
ATTRIBUTE	appear to be wrought from burnished gold and silver

Insect colours serve many purposes. Greens and browns act as camouflage against living and dead leaves, tree trunks, branches and twigs. Bright yellow, orange and red, often marked with black, warn that an individual is poisonous or might sting. But the brightest and most spectacular colours do neither. Metallic glints of bronze, blue, green, red and violet occur in many beetles, bees, wasps, flies and, of course, butterflies (see page 48). The most astonishing of these are the brilliantly shining golden chafers, Plusiotis species, of Central and South America.

Metallic sheens are not colours in the conventional sense of a pigment or colourant on the surface of the animal. The red of a ladybird, for instance, appears because the yellow, green and blue wavelengths in sunlight are absorbed and only red light reflects back into the eye of the beholder. The metallic shine of the golden chafers, by contrast, is caused by the white sunlight being broken, much as it is when shining through a diamond, to give a series of rainbow glints.

Seen through an electron microscope, the surface of the beetle is revealed to be covered with minute parallel grooves. These reflect certain portions of the light at the precise angle to shine like polished metal, while absorbing and scattering other wavelengths.

Shining colours are not just for showing off to a potential mate, although this is important for many butterflies. One of the main purposes, ironically, may be to avoid attention. In bright sunlight, against wet mud or in the dripping rainforest canopy, metallic glints are surprisingly confusing to the eye of a predator, which searches for images based on shape.