Small bee species can have remarkably acute vision, proving that large eyes are not always necessary for clear vision.
Bees use vision in many aspects of their daily lives. They rely on what they see to find food, return to their nests, avoid predators, and spot other bees.
For decades, honeybees have been the primary species used to study bee vision. However, with over 20,000 known bee species, their eyes can function quite differently. New research shows that some small bees are able to discern surprisingly fine detail. In some tests, their vision was even sharper than that of worker honeybees.
Researchers from Lund University studied three species of solitary bees and one species of bumblebee. Solitary bees live primarily alone, rather than forming large colonies like honeybees.
The team studied the bumblebee Bombus terrestris, the woolly bee Anthidium manicatum, the four-striped flower bee Anthophora quadrimaculata, and the Australian blue-striped bee Amegilla murrayensis.
They then compared these results with earlier measurements taken on worker and male honeybees, called drones. This allowed them to see how different bee species behave under similar testing conditions.
Bees have complex eyes composed of many small visual units. Each of these neurons contains light-sensitive cells called photoreceptors, which convert light into electrical signals processed by the nervous system.
The researchers recorded electrical signals from individual photoreceptors in living bees. The insects were placed in front of a bright computer screen while small dark objects moved across it.
The team varied the size and position of these objects to observe how each photoreceptor responded. This allowed them to assess how clearly the cells could discern fine visual details.
They also measured the size of a moving object that produced a signal strong enough to stand out from the normal electrical noise in the cell. This gave the researchers another way to measure how well each bee could detect tiny targets.
All four newly studied species showed higher photoreceptor resolution than worker honeybees. This was true for both males and females.
The clearest response was observed in male and female blue-striped bees. Males of the Anthidium and Anthophora species also demonstrated particularly high visual resolution. In these measurements, a smaller visual angle means the photoreceptor can discern finer details.
In some individual cells of male Anthidium and Anthophora bees, temperature values reached close to one degree, with similarly high values observed in blue-striped bees. The results refute the idea that bees require large body size or large eyes for acute vision. Smaller species may achieve high visual acuity through other features of their eyes.
The Australian blue-striped bee demonstrated one of the most impressive results. It is able to detect very small moving objects almost as well as honey bee drones, despite being significantly smaller.
“We were particularly surprised that the small blue-striped bee, despite its much smaller size, was able to detect objects as well as honey bee drones,” said Elisa Rigosi of Lund University.
Honey bee drones are known for their acute vision, as they need to locate and pursue queens during mating flights. Their large eyes are well adapted to detecting small moving targets.
The blue-striped bee demonstrated similar target detection results, despite having smaller eyes. This suggests that eye size alone does not determine a bee’s visual acuity.
The research team examined several parts of the eye to understand why different species exhibit different behavioral characteristics. They measured the overall size of the eye, the size of individual surface lenses, and the density of the visual units within the eye.
They also measured the rhabdom—the light-collecting structure within each photoreceptor. Its width can influence the balance between light collection and the perception of fine detail. Overall eye size did not have a clear relationship with photoreceptor acuity. Surface lens size also did not fully explain the differences between species.
Rhabdom width showed a clearer pattern.
Dimensionality. Narrower rhabdoms were associated with sharper spatial vision, while wider rhabdoms can collect more light but may reduce image detail.
The results suggest that there is more than one way to develop a highly efficient eye in bees. Different species appear to balance eye structure, light sensitivity, and image detail differently.
Male bees of the genus Anthidium appear to pay close attention to fine visual details.
Honey bee drones combine large surface lenses with dense visual scanning, while blue-striped bees achieve high target detection accuracy thanks to smaller eyes and low electrical noise in the photoreceptors.
David O’Carroll, a professor of biology at Lund University, also participated in the study.
“There is no single recipe for good vision in bees. Different species have achieved different combinations of traits that ensure high visual acuity,” said O’Carroll.
These differences suggest that bee eye shape may depend in part on the tasks each species performs. Bees pursuing mates, defending territories, or navigating diverse environments may use different types of visual systems.
Most of our knowledge about insect vision comes from studying a small number of well-studied species, particularly honeybees. Studying a larger number of species may reveal abilities that would otherwise remain hidden.
“Bee vision is much more diverse than previously thought. By studying more species, we see that evolution has developed a variety of ways to achieve high visual efficiency,” says Rigosi.
These findings may also help us understand how small visual perception systems can operate effectively. Different “bee eye” designs may offer useful ideas for artificial vision systems or small robots that require compact and energy-efficient sensors.
However, these findings do not mean that every small bee has sharper vision than a honeybee. The researchers selected a limited group of species, so their results cannot fully describe all the thousands of bee species worldwide.
Laboratory studies also cannot fully replicate the conditions bees encounter outdoors. The computer screens used in the experiments were much dimmer than bright sunlight, so some bees were able to detect even smaller targets in the wild.
Direct electrical noise measurements were available for only 27 percent of photoreceptors of each species and sex. Where direct measurements were unavailable, the researchers used the average noise level for the given group.
Understanding how widespread these patterns are will require more species and more detailed maps of the various parts of the bee eye. For now, the results indicate that bee visual acuity does not depend on any simple feature, such as large eyes. Different combinations of eye size, cell structure, visual sensitivity, and light sensitivity can contribute to good vision.
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