Most bee species, including common honeybees and bumblebees, do not see effectively at night. These bees are active during the day and rely on sunlight for their activities. While the majority of bees are diurnal, certain fascinating exceptions exist. These exceptions have evolved unique adaptations to navigate and forage in low-light conditions.
The Marvel of Bee Vision
Bees possess a sophisticated visual system adapted for their daytime activities. They have two large compound eyes, each composed of thousands of individual lenses called ommatidia, which provide a wide, almost 360-degree field of view. These compound eyes are adept at detecting movement, color, and shades, allowing bees to perceive their environment and navigate efficiently.
In addition to their compound eyes, bees also have three simple eyes, known as ocelli, located on the top of their heads. These ocelli primarily function as light detectors, helping bees gauge light intensity and maintain flight stability and orientation. Bees perceive a different color spectrum than humans, seeing ultraviolet (UV) light, blue, and green, but not red. Many flowers display UV patterns, invisible to humans, which act as “nectar guides” to direct bees toward pollen and nectar sources. Bees can also detect polarized light in the sky, even when the sun is obscured, using it as a compass for navigation and communicating directions to their hive mates.
Why Night Vision is Limited for Most Bees
The visual systems of most bee species, such as honeybees and bumblebees, are optimized for bright, daytime conditions. Their compound eyes, while excellent for detecting color and movement in ample light, lack the specialized structures necessary for efficient vision in low light. These structures include photoreceptors with high sensitivity and large light-gathering components that would allow them to function in dim environments.
Unlike many nocturnal animals, typical bees do not possess adaptations like significantly larger ommatidia or a tapetum lucidum, a reflective layer behind the retina that enhances light capture in darkness. Consequently, their visual capabilities decline sharply as light levels decrease. This physiological constraint means that most bees struggle to resolve spatial details or distinguish colors once darkness falls.
The World of Nocturnal Bees
While most bees are active during the day, about 1% of known bee species, approximately 250 worldwide, are genuinely nocturnal or crepuscular, meaning they are active at dawn and dusk. These bees have evolved specific adaptations to thrive in low-light conditions. Examples include certain sweat bees, such as Megalopta genalis, and the Indian Carpenter bee.
These nocturnal species often possess larger ommatidia, the individual units of their compound eyes, which are more effective at gathering the scarce light available at night. Their ocelli, the simple eyes, are also notably larger in proportion to their body size compared to diurnal bees, enhancing their sensitivity to dim light. For instance, the eyes of Megalopta genalis are significantly more sensitive to light than those of diurnal bees, allowing them to navigate and forage effectively even in conditions as dim as starlight under a forest canopy. Some nocturnal bees, like the Asian giant honeybee (Apis dorsata), can even perceive colors in very low light.
Bee Behavior in Low Light
As daylight diminishes, most bee species, including honeybees, cease their foraging activities. They typically return to their hives or nests before dusk, relying on the fading light to guide them back. Once inside, they spend the night engaged in various essential colony maintenance tasks.
These activities include processing nectar into honey, caring for larvae, and cleaning the hive. Bees also form a cluster, especially in cooler temperatures, to regulate the hive’s temperature and maintain warmth. While some bees might use other senses like smell or memory for short-distance navigation if caught out after dark, extensive foraging or long-distance travel is not possible for them once their vision is compromised by darkness.