Jayden Cochrane, of Balclutha Primary School, asks :-

Do insects see colour?

Craig Johnson, a veterinary neurophysiologist, at Massey University, responded.

Insects have several kinds of eyes with a variety of different functions that vary from some with only the ability to detect the general direction of light and darkness right up to others that can generate a detailed visual image. The eyes that are most similar to our own are the compound eyes and these are made up of many separate units called ommatida. Each unit collects light from a different place and sends its information to the brain to be built into an image. Most insects are dichromatic. That means that they have two different kinds of pigment responding to different wavelengths of light. This gives them the ability to tell some colours from others, but not all.

Some insects such as honeybees are trichromatic and have pigments responding to three wavelengths of light, but these are not usually the same wavelengths that we see. The honeybee has pigments responding to blue, green and ultraviolet light and so the colours that it sees are very different from those that we see. In addition to seeing different colours, honeybees can see the polarisation of light. Light from the Sun is polarised as it travels through the atmosphere and honeybees use this as a compass to enable them to navigate.

Being able to see ultraviolet light that most animals can't detect can be very useful for communication. For example, female cabbage butterflies have scales on their wings that reflect ultraviolet light. These reflections make them very obvious to other butterflies and help in attracting mates, but cannot be seen by predators such as birds.