Biologists have discovered that bumblebees can distinguish between short and long light flashes to find food. This ability, reminiscent of recognizing Morse code signals, was previously thought to be unique to vertebrates.

The Importance of Temporal Information for Animals

The ability to process temporal signals plays a crucial role in animal survival. It helps them plan foraging, communicate with others, and avoid predators. For example, hummingbirds remember how quickly nectar appears in certain flowers so they can return at the right time. Honeybees perform a complex "dance" in which the duration of their movements indicates the distance to a food source.

Mechanisms of Time Perception

Animals perceive time on various scales—from multi-year seasonal cycles to fractions of a second. Longer cycles, such as the alternation of day and night, regulate internal biological clocks based on protein synthesis. However, these mechanisms are too slow to explain the ability to distinguish short intervals measured in seconds. Until recently, it was believed that only vertebrates with developed brains—such as monkeys, rats, or pigeons—possessed this skill.

The Question of Insect Capabilities

It remained an open question whether insects, with their miniature nervous systems, could handle such tasks. Despite having brains smaller than a cubic millimeter, bumblebees display complex behaviors. Studying their abilities helps us understand the fundamental principles of nervous system function.

The Bumblebee Experiment

Biologists decided to test whether Bombus terrestris bumblebees could distinguish the duration of visual signals to make decisions. The results were published in the journal Biology Letters.

For the experiment, a special maze with three compartments was created, each containing a monitor. On the screen, bumblebees were shown two flashing yellow circles: one flashed with short intervals ("dot"), the other with long intervals ("dash"). One signal was associated with a reward—a drop of sugar solution—while the other was linked to a punishment in the form of a drop of bitter quinine solution. To ensure the bees focused on the signal rather than the reward's location, the positions of the "dot" and "dash" were constantly changed.

Training continued until a bumblebee made 15 correct choices out of 20 attempts. Then came the testing phase, where plain water replaced the reward and punishment. This allowed researchers to confirm that the insects were responding specifically to the duration of the flashes, not to scent or other cues.

Two Stages of the Experiment

The experiment was conducted in two stages. In the first, the total duration of illumination for the "long" and "short" signals differed (for example, the "long" signal was lit for five seconds, the "short" for one). In the second stage, the task was made more difficult: the total duration of illumination for both signals was the same, but the frequency and duration of individual flashes differed.

Research Results

Bumblebees successfully completed the task in both experiments. They learned to reliably identify the correct signal associated with the reward, even when the total amount of light from both circles was the same. In the first experiment, 16 out of 20 bumblebees, and in the second, 17 out of 21, performed above chance. This proves that the insects made decisions based specifically on the duration of individual flashes, not on overall brightness or flash frequency.

Conclusions and Significance of the Study

The study showed that bumblebees possess complex abilities to process temporal information, which were previously thought to be inaccessible to insects. These skills are not linked to innate foraging strategies, since bumblebees do not encounter flashing signals in nature. It is likely that they use more universal learning mechanisms.

Scientists suggest that similar neural circuits may be responsible for both time perception and spatial orientation, such as when estimating flight speed. Studying such efficient "computational" systems in insects can help us better understand how the brain works at its most fundamental level.