Bees are primary pollinators for countless flowering plants. Their work ensures the reproduction of many plant species, including crops. Bees are not drawn to flowers randomly; they are guided by specific signals, with color playing a primary role in directing them toward nectar and pollen sources.
How Bees Perceive Color
Bees possess a unique visual system, differing significantly from human vision, which optimizes their foraging efficiency. Like humans, bees have trichromatic vision, basing their color combinations on three primary colors. However, while human vision relies on red, green, and blue photoreceptors, bees’ vision centers on ultraviolet (UV) light, blue, and green. Their eyes contain three types of photoreceptors that are most sensitive to short-wavelength (UV, peaking around 344 nm), middle-wavelength (blue, peaking around 436 nm), and long-wavelength (green, peaking around 544 nm) light.
This specialized vision allows bees to see a spectrum from approximately 300 to 650 nanometers, including ultraviolet light invisible to human eyes. Their compound eyes, composed of thousands of tiny lenses (facets), enable them to process images and colors rapidly, up to five times faster than humans. Each facet captures a small part of the visual field, forming a comprehensive picture. Additionally, bees have three simple eyes (ocelli) that help them gauge light intensity and maintain orientation during flight.
Colors That Attract Bees
Bees are most strongly attracted to specific colors that signal the presence of nectar and pollen. Blues, purples, and violets are particularly appealing to bees because these colors fall within the wavelengths to which their photoreceptors are highly sensitive. Many violet-blue flowers produce high volumes of nectar, reinforcing bees’ preference for these hues. Some flowers exhibit “bee’s purple,” a combination of yellow and ultraviolet light, creating a color humans cannot perceive but is highly attractive to bees.
White and yellow flowers also draw bees, especially if they reflect ultraviolet light. Many flowers, including those appearing white or yellow to humans, possess distinctive ultraviolet patterns, often called nectar guides. These UV patterns act like a landing strip, directing bees toward the flower’s center where nectar and pollen are located, making foraging more efficient. Examples of flowers that attract bees with these colors include lavender, salvia, echinacea, and aster varieties.
Colors Bees Avoid
Bees generally avoid colors they cannot perceive well or that do not indicate a reward. Bees largely do not see red, as they lack the specific photoreceptors sensitive to red wavelengths. Consequently, red flowers often appear as black or gray to a bee. While bees might visit red flowers if they reflect ultraviolet light, red itself is not a primary attractant. Similarly, black is less attractive because it absorbs all light, making it difficult for bees to distinguish shapes and patterns for navigation and foraging.
Beyond Color Other Floral Cues
While color is a significant factor, bees also rely on other floral cues to locate and identify flowers. Scent plays a crucial role as a long-distance attractant, guiding bees to flowers before they are within visual range. Flowers emit complex mixtures of volatile compounds, creating unique fragrances, and bees learn to recognize scents associated with rewards. Some floral scents, such as those containing linalool, are particularly effective at attracting pollinating insects like bees.
Beyond scent, nectar guides, often invisible to the human eye, provide precise directions once a bee is close to the flower. These patterns, often visible only in ultraviolet light, act as bullseyes or runways, leading the bee directly to the nectar source. Flower shape and size also serve as secondary cues, influencing how easily a bee accesses pollen and nectar. Open flowers with visible pollen and nectar are generally more appealing, allowing bees to efficiently gather resources.