Bumblebees use light to tell time, study finds

Bumblebees spend much of their lives weaving through fields in search of food, yet new research shows their skills stretch far beyond color cues and floral scents.

Scientists have discovered that these small insects can tell the difference between short and long flashes of light and then use that information to find better feeding spots. The finding may change how you think about the tiny animals that buzz past you in a garden.

Timing shapes the lives of many creatures. Hummingbirds return to blossoms when nectar is likely to be replenished. Crickets send messages to each other through chirps that vary in length. Honeybees rely on the famous waggle dance, which encodes distance and direction through a pattern of movements.

Some of these rhythms unfold over days, while others happen in fractions of a second. Shorter intervals play a key role during flight, feeding and communication, and large animals such as rats and pigeons have long been used to explore how brains track these fleeting moments.

Much less has been known about how insects read time on such a fine scale. Earlier tests suggested that wasps could link different rewards to intervals lasting several minutes and that bees could expect a treat after a delay of a few seconds. But scientists had not yet shown that insects could judge the duration of visual signals that change in less than a second.

That scientific gap motivated researchers at Queen Mary University of London to ask whether bumblebees could sense how long a flash of light lasts and use that information when choosing food. Ph.D. student Alex Davidson and Senior Lecturer Dr. Elisabetta Versace led the project, which used Bombus terrestris bees raised in a wooden nest box kept at a steady temperature on a normal day and night cycle.

Each colony lived in a hive linked by acrylic tunnels to an observation area and a testing room. Only one forager from a colony was tested per day. In the test room, three small compartments faced a monitor that displayed bright yellow circles on a dark background. These circles blinked on and off in patterns the researchers controlled. Two stimuli appeared at a time, one pulsing for a longer duration and the other flashing briefly. Beneath each circle was a small chip filled either with sugar water or a bitter quinine solution.

Before the experiment started, each bee explored the setup while sipping sugar placed near the screens. Once the bee learned that food could be found in the test compartments, training began. She was led to a compartment, held briefly behind a clear panel so she could watch the flashing lights repeat their full cycle, and then allowed inside to choose one of the feeding chips. A choice was recorded the moment she touched one of the chips.

If she selected the light paired with the correct duration, she tasted sugar. If she chose the wrong one, she received the bitter liquid. Scientists switched the left and right positions of the stimuli between trials to prevent bees from simply guessing the same side. Training continued until the bee made at least 15 correct choices out of her last 20 attempts. If a bee began choosing the same side twice in a row incorrectly, she received special correction trials that encouraged her to break the habit.

The research team used two types of timing tests. In the first, bees had to choose between a short or long flash where the longer flash also produced more total light. For example, during a 10 second cycle, the long flash stayed on for 5 seconds while the short one stayed on for only 1 second. In another version, the cycle lasted 5 seconds, with long flashes of 2.5 seconds and short flashes of 0.5 seconds.

The second experiment presented a tougher challenge. The overall amount of light each stimulus produced per cycle was made equal, even though one flashed in short bursts and the other in long ones. That ruled out the possibility that bees solved the problem by noticing that one circle simply looked brighter.

After training, each bee entered a testing stage with 15 trials where both chips contained only water. Refresher trials with sugar and quinine were mixed in to keep the bees interested, but the water-only trials showed whether they were choosing based on timing alone.

The results were striking. In the first experiment, bees strongly chose the correct flash pattern at rates above chance. It did not matter whether sugar had been linked to the short or long flash; bees learned either pattern equally well. One small effect showed that bees performed a bit worse in the compartment farthest from the nest, suggesting fatigue or distance might play a minor role.

The second experiment confirmed that the insects tracked the duration itself rather than the total light. Even when short and long flashes produced the same overall brightness, bees still picked the correct stimulus more often than expected by chance. This finding strongly pointed to real timing perception.

Across both experiments, the majority of tested bees showed accurate choices. Some individuals were more decisive than others, but the group effects were clear. Bees were not simply guessing. They were reading the length of the flashes and using that information as a guide.

The work suggests that bumblebees have flexible timing skills that go beyond anything they would naturally encounter. The insects do not see flashing circles in nature. Yet they were able to use the duration of these artificial signals to find better food sources. Versace said this ability may reflect a general timing system that evolved for other needs, such as tracking how visual scenes change during flight.

The discovery also raises questions about how such small brains, each less than one cubic millimeter, handle time. The slow biological clocks involved in day and night rhythms cannot explain these short intervals. Scientists have proposed models involving internal pulses or patterns of neural activity that unfold over time. With this new research, insects can now be used to test such ideas directly.

Davidson said, “We wanted to find out if bumblebees could learn the difference between these different durations, and it was so exciting to see them do it.” He noted that their success shows that time processing may be a basic property of neurons rather than a skill reserved for large brains.

Research findings are available online in the journal Biology Letters.

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