The butterfly
The secret of its colour
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| White light is made of many colours. Insects can seperate white light into its component colours through a number of techniques to produce a vibrant, colourful appearance. |
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The wonderful colours and patterns displayed on the wings
of butterflies are composed of a delicate and intricate arrangement of
scales on the wing surface of the insect.
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Each scale is placed such that
it overlaps with the one next to it, just like roof tiles.
The scales are hardened external growths of the cells that cover the wing.
The colours of the scales can be of two distinct kinds: pigmentary and
structural. The majority of the pigmentary colours are formed by a pigment
called melanin. Blacks, greys, brown, brownish shades of red and yellow
are all forms of melanin. Melanin is no stranger to us, it is the pigment
which colours our skin. |
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Striking colours, such as the iridescent and the metallic
ones, the greens and blues, are due not to chemical pigments, but to tiny
structures on the surface of the scale. These structures bend and separate
light into its different component colours, much like a prism bends white
light into the colours of the rainbow. The shape and pattern of these
structures, as shown on the left, determines the colour. |
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Different structures on the scale surface
create different colours. The images on the left show the some of the colours that are produced by the varied ridge patterns on the wing. Notice how a slight change on the pattern changes the spread of the reflected light. |
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CDs interfere with the light to create many different colours in similar ways as the ridges and grooves on the scales of some of the more exotic butterflies shown below.. |
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Investigate how white light
can be separated into different colours?
How is a rainbow created?
What other insects use and manipulate light to
their advantage?
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