Bumblebees are important pollinators, facilitating the reproduction of many plants, including crops. Their role in ecosystems and contributions to biodiversity make them a subject of scientific interest.
The Bumblebee’s Eye Count
Bumblebees possess a total of five eyes, categorized into two distinct types. Two large compound eyes are located on either side of their head. Complementing these are three smaller, simpler eyes, known as ocelli, which are arranged in a triangular pattern on the top of their head.
How Bumblebee Eyes Function
The two types of eyes in bumblebees perform specialized tasks, contributing to their overall visual capabilities. The large compound eyes are composed of thousands of individual visual units called ommatidia. Each ommatidium contains its own lens and light-sensing cells, collectively creating a mosaic-like image of the surroundings. This design provides a wide field of view, enabling efficient motion detection.
These compound eyes are sensitive to specific wavelengths of light, including ultraviolet (UV), blue, and green. Bumblebees perceive UV light as a distinct color, useful for identifying flowers. Many flowers display UV patterns, often referred to as “nectar guides,” that direct bees toward pollen and nectar sources. The ability to process visual information quickly, at a flicker fusion frequency of around 110 Hz, also allows bumblebees to navigate and avoid obstacles during their rapid flight.
The three ocelli, or simple eyes, on the top of the bumblebee’s head, serve a different visual function. These single-lens eyes do not form detailed images, but they are highly sensitive to changes in light intensity. Ocelli help bumblebees detect light levels and orient themselves, especially during flight. They are particularly sensitive to ultraviolet and green wavelengths, assisting with flight stability and gauging the position of the sun.
Information from both the compound eyes and the ocelli is integrated by the bumblebee’s brain for a comprehensive understanding of their environment. This combined visual input is essential for behaviors such as foraging, navigating, and evading threats. The detection of polarized light by both eye types further aids in navigation, allowing bumblebees to maintain their direction even on cloudy days when the sun is not directly visible. This visual system, alongside other senses like smell, allows bumblebees to locate food sources and return to their nests with precision.