The butterfly

The secret of its colour

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.

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.





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.
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.

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.


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..
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?

Home of butterflies

Light breaking structures on the surface of the scale. The grooves on the surface of a CD interfere in a similar way with light and produce different colours. Click to see a 120Kb movie of CD in the light.