Ultraviolet Vision – The Bees Knees

Not only are bees preferential to the color and shape of flowers, they can also see a range of ultraviolet colors! The study of bee cognition began back in the 1900’s with the Austrian scientist Karl von Frisch. Frisch won the Nobel prize for his work with honeybees, and his experiments resulted in the super cool discovery of bee color recognition.

In the 1900’s, Karl noted two important things about bees: they revisit visit hundreds of types of flowers, and not all flowers that bees visit are at all the same. Flowers can vary in how much pollen and nectar they provide, and some flowers, such as orchids, offer bees no food at all. Thus, is can be concluded that bees purposely choose not to visit only one type of flower, and for good reason. After all, if a bee is getting quality food for her colony, then she needs to quickly learn which flowers are worthwhile to visit.

Using this information, Karl von Fritch designed his experiment. He most likely knew that bees were good subjects for associative learning. Just as Pavlov’s dogs learned that a sound predicted food, a bee learns that a particular flower offers better nectar than surrounding flowers. First, Fritch trained bees to collect a sugar water solution off of blue colored cards. He then placed the blue cards among cards that ranged from a light grey to a dark grey. The darkest grays resembled the same dark coloration as the blue cards. Thus, the bees landed on one of the grey cards, right?

Not quite – the bees chose to land on the blue cards, thus proving that they can perceive color. This theory was tested again with other colors such as: orange, green, violet, and yellow. Just as before, the bees chose the colored cards versus the grey scaled cards. However, they could not distinguish the color red.

Following Karl von Fritch’s studies, scientists have proven that bees re-visit flowers based on shape, temperature, and even electrical field. What I find most fascinating is the fact that bees can see the ultraviolet. So how do bees use this vision superpower? In 1927, Alfred Kühn used irradiating squares that included ultraviolet light in a similar study to Karl’s.

 

The experiment worked because like humans, bees are trichromatic, meaning that they have photoreceptors within the eye to create color combinations. Humans base their color combinations on red, blue and green; bees, on the other hand, base their combinations on ultraviolet light, blue, and green. Unfortunately, this is why bees are unable to see the color red. However, bees will choose to pollinate poppies, but only if the flowers have a reflective ultraviolet light. Bees also see a combination of yellow and ultraviolet light – the color that most likely attracts bees to flowers besides purple.

 

Finally, it helps that bees can focus on individual flowers, even when they buzz around from plant to plant so rapidly. They also pick up on flower petals that change color depending on their angle, also known as iridescence. When bees see these shiny petals in the UV spectrum, they associate the perceived colors with sugar. Thus, the shinier, violet, and UV spectrum based flowers are more attractive to bees as a whole. I’m sure if humans had this special vision, a field of flowers would look like it was colored in glow-in-the-dark glitter!

– Sophie Kovalcik