The way bees see is their superpower. Their unique vision gives them the ability to find nectar- and pollen-rich flowers.
How bees see
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.
Evening primrose in ultraviolet light.
Evening primrose in visible light.