Pollinators’ view

Insects don’t see light the way we do

Insects see the world very differently from the way we do; and their vision varies from species to species. Some cave dwelling insects do not have eyes, others can distinguish between light and dark while predators such as dragonflies have good eyesight and can even detect minute motion.

An insect eye can be simple or compound and many species can detect infrared and ultraviolet waves which are beyond our range of vision and so can see things that we cannot.  

Compound eyes are made up of small structures known as ommatidia. Each ommatidium is able to form an image and the insect brain joins all the images together to form a single picture. 

The more ommatidia present the more detail that can be seen. 

Some dragonflies can have up to 30,000 ommatidia in each eyeball and are able to see small insects such as mosquitoes flying at a distance. Even flies such as the housefly have good sight. That is why swatting a fly is so difficult. But to get such vision the ommatidia must be as long as possible. That is why insects with good vision have large bulging eyes. If humans had to use the same system as insects they would need one-metre large eyes to see the same as they do with their simple eyes.

For some insects, the ability to detect different colours is also important. Honey bees can see in the ultraviolet range of the spectrum. Using a special camera, scientists have made pictures of flowers using ultraviolet rays. The results have shown the bees see flowers differently from the way we see them. 

Although we cannot know exactly how bees see the pictures have shown that many petals have lines which guide the bees to the nectar. It also helps them to distinguish between the flowers of different species which to us might look the same.

It is believed that the Monarch butterflies which migrate more than 4,000 kilometres in the American continent use ultraviolet light from the sun to navigate. 

This article was published in The Times on 17.10.2012