How bees use their unique vision to search for food and find their way home
The way bees see is their superpower. Their unique vision gives them the ability to find nectar- and pollen-rich flowers.
Bees have two different types of eyes which do different jobs. On top of their heads are three small, single-lensed eyes called ocelli. Bees use them to see flower colours with ultraviolet light, judge light intensity, navigate and keep orientated.
They also have two much larger compound eyes with thousands of facets or tiny lenses. Each facet is connected to a cone with eight cells called photoreceptors. In each cone, there are two receptors for each of the colours blue, yellowy-green and ultraviolet. Information from all the facets is collated by the bee's brain and makes a mosaic picture of its surroundings. It sounds complicated but it's amazingly fast. Bees perceive colour three to five times faster than humans. This means they can see individual flowers blowing in the wind even while flying.
Humans also have three sorts of photoreceptors but ours detect red, blue and green. Bees can't see red because they don't have the right receptors, but they do see ultraviolet markings on petals that are invisible to humans.
Plants have evolved to exploit the way bees see. Flowers pollinated by insects have contrasting colours that stand out from foliage around them. In contrast, wind-pollinated flowers are often similar in colour to leaves and stems as they don't need to be detected by sight.
Flowers that rely on bees have ultraviolet markings on the petals around the pollen-rich stamens and nectaries which produce nectar. Bees are quick learners. They associate the markings with food so go straight for the ultraviolet bull's-eye blotches and lines that lead to the sweet nectar within.
Bees also detect the patterns of polarised light in the sky and use them to find their way back to the hive even if the sun isn't shining and at different times of the day.
A bee that has found a good source of nectar or pollen can let the other foraging bees know where to go. If the food is within 50-100m of the hive, the bee does a round dance, quickly turning clockwise and anti-clockwise and the surrounding bees follow along.
If the food is further away, the foraging bee does a waggle dance, turning in a semi-circle then going back to the beginning waggling her abdomen. The angle gives information about the direction of the food and the time going across the circle gives the distance.
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HOW TO BRING BEES INTO YOUR GARDEN
• Plant blocks of the same flower at least a metre wide so they are easy to find and the bees don't need to move very far between each bloom.
• You don't need to plant a dedicated garden plot for bees. Just include bee-friendly plants in among the vegetables, flower beds and around fruit trees. Grow flowering trees, shrubs and hedges.
• Plan a succession of flowers so there is food available all year round. Pollen is rich in protein and is especially important in spring when lots of young bees are raised to increase the hive population numbers. Both pollen and nectar are needed over summer. Nectar is stored over autumn as honey to provide food for the winter.
• Ornamental flowers, vegetables, herbs, shrubs and trees – native and introduced – can all provide bee food. So can weeds. Be mindful of bees before spraying or eradicating flowering weeds. Gorse and broom, for example, supply pollen in early spring when there is a shortage.
• Simple, open, single traditional flowers give easier access to pollen than highly modified, double-petalled modern cultivars. So do the flat-topped flower clusters on members of the Apiaceae family (carrots, fennel, parsley, coriander, parsnip) which act as landing pads for pollinators.
• Bees need water too. Provide clean, shallow water with a landing platform for easy access and a beach gradient so bees can climb out if they fall in.
• Don't spray at all or if you must, spray early in the morning and at sunset when bees are not around. Don't spray when plants are in flower and don't let spray drift contaminate bees' drinking water.
• Bees find their hive using visual cues. If there are several hives side by side, bees will find their own home more easily if the hive boxes are painted in different colours.
The two galleries below will show you the different pollinators to look out for when bee-spotting!
- NZ Gardener