Vision as we understand it is based on light. For humans and many other animals, that light is called visible light and it falls in a specific region of the electromagnetic spectrum.
The electromagnetic spectrum is the full range of electromagnetic radiation, a type of energy that travels in waves. This spectrum includes radio waves, microwaves, infrared radiation, visible light, ultraviolet light, X-rays, and gamma rays.
Each type of radiation is characterized by the amount of energy and wavelength. High-energy waves have short wavelengths while low-energy waves have long wavelengths.
Visible light falls near the middle of the spectrum, with wavelengths between 700 and 400 nanometers (nm). Radio waves have wavelengths of 1000 meters to 1 centimeter. The wavelength range of ultraviolet light is 400 to 10nm.
The different wavelengths of visible light correspond to the colors that we see due to the reflection of waves off of objects. Something that appears green reflects wavelengths in the green region of the visible spectrum.
Bees also see the reflections of electromagnetic waves, but their vision is a little different from ours. Here, we’ll cover the part of the electromagnetic spectrum that bees can see, the differences between bee vision and human vision, a little bit of bee anatomy, and why it’s so good to see like a bee.
What spectrum of light do bees see?
Bees see light between 600 and 300nm. This means that they miss some visible light (between 600 and 700nm), but they also gain some ultraviolet light (between 300 and 400nm). The segment of the visible spectrum that they’re missing is red.
Bees cannot see the color red. Beekeepers use this to their advantage. They use red lights to monitor their bees. This color works well as domestic bees’ lighting because it won’t disturb them.
The inability to see the color red doesn’t mean that all red flowers are essentially invisible to bees, though. They can detect edges very well, so they can see a red flower, but it doesn’t look red to them. Early experiments showed that bees can’t pick a single red square out of a collection of squares that are shades of gray.
Within their range of color vision, bees seem to prefer blue, violet, and purple over colors such as green, yellow, and orange. Interestingly, much of iridescence appears in the ultraviolet portion of the spectrum. Thus, bees can see the shimmer of iridescent objects often better than humans.
Difference between bee and human vision
Bee vision differs quite a lot from human vision.
In addition to their ability to see ultraviolet light (which comes with a heightened ability to detect iridescence), bees can also see polarized light.
Light becomes polarized as it passes through the atmosphere in a process called scattering. Sunlight is initially radiated in all directions, but this changes when it reaches our atmosphere. It hits gas molecules, which then shoot the radiation out at 90o to the direction of the light source. This polarized light only travels in that single direction. Thus, polarized light shines in a circle around the sun. We can’t see it without special equipment. However, bee eyes have special equipment built in.
Bees have five eyes: three simple eyes on the tops of their heads and two compound eyes on either side. The three eyes on top of their heads are called ocelli (which literally translates to “little eyes” in Latin).
Each ocellus has a single lens that gathers light, including ultraviolet light. These eyes help bees stay oriented in space and help them navigate by allowing them to judge the intensity of light.
This includes polarized light. The intensity of polarized light is an indicator of the sun’s position. Where polarized light is the most intense, you will find the sun perpendicular, even on overcast days.
Bees’ compound eyes are composed of thousands of little lenses, called facets. Each facet caps an individual tube that contains a cone of light-capturing and pigment cells. The tube and facet together are called an ommatidium.
There are eight light-capturing cells within each ommatidium, four of which respond to yellow-green light, two that respond to blue light, and one that responds to ultraviolet light. Each ommatidium takes in a small part of the bee’s vision. When all the parts are put together in the bee’s brain, the image that results looks like a mosaic.
In contrast, people have just two eyes. Instead of a tube leading from our lens to our optic nerve, we have an eyeball with pigment cells at the back.
Our lenses focus light from a much wider field than a single ommatidium onto the retina (where the pigment cells are located). Thus, we see a smooth image instead of a mosaic. We also can see the red light and cannot see ultraviolet or polarized light, making the world we see very different from that seen by a bee.
Advantages of seeing like a bee
The way bees see the world is absolutely necessary for their way of life.
For one thing, flowers have ultraviolet patterns on their petals that are only visible to animals that can see ultraviolet light. These patterns differ from flower to flower and guide bees to the center of the flower, where the nectar and pollen are.
A flower’s center absorbs ultraviolet light rather than reflecting it so that it stands out even more starkly from the rest of the flower than it does to us.
It’s also easier for bees than people to tell the difference between flower species because they display different ultraviolet patterns even when they look similar in the visible spectrum.
Despite the fact that bees don’t see the color red, they will still forage on red flowers due to their ultraviolet patterns.
Ultraviolet light is so important to bees that if they are deprived of it, they won’t leave the hive to forage until they are nearly at the point of starvation.
Polarized light is also critically important for bees. They use it to navigate. They know in which direction to fly by recognizing the angle of that direction relative to the sun.
Recall that the highest intensity polarized light is observed at 90o from the sun’s position. Once bees know where the sun is, they can recognize the direction in which they need to fly. Honey bees can even communicate this information to each other using a dance in which different movements correspond to different instructions.
Bees have a remarkable vision. They see in parts of the electromagnetic spectrum that we can’t and they see polarized light.
The ultraviolet spectrum is useful to bees because flowers have varying ultraviolet patterns that help bees recognize them and that guide them directly to the flower’s nectar and pollen center. Polarized light helps bees navigate by helping them determine their position in relation to the sun even when they can’t see the sun directly.
We consider the inability to see red a disadvantage, but for bees, it’s no problem. While it might seem strange to use to view the world in mosaic, to a bee, it’s completely normal.
We hope this has given you some insight into a bee’s world.