Colour is key in insect world

11:35am Monday 7th April 2008

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PEOPLE often wonder why mammals are not so brightly coloured as birds and insects.

The reason is that mammals are colour blind and birds and insects are not.

Vision involves two types of cell. Rod shaped cells deal with black and white vision whilst cone shaped cells deal with colour. Mammals eyes only have rods.

The eyes of birds and insects are not similar apart from the cells.

Birds have two eyes each with a lens and a receptive retina.

Insects only seem to have two, but these are rightly described as compound eyes.

Each can contain as many as 25,000 little lenses and so insects like butterflies have excellent vision, but should be compared to a jigsaw.

If insects had to see an optician the poor practitioner would soon be driven mad!

One thing is sure, insects such as butterflies are perhaps even more sensitive to colour than we are.