Bees that appear violet or purple display this coloration in one of two main ways: either through a permanent, light-manipulating biological structure or a temporary hue gained from their foraging activity. This dual reality explains why some bees consistently possess a stunning, metallic purple sheen, while others momentarily display a vibrant purple hue that vanishes after they return to their nest. Understanding the difference between these two phenomena reveals the intricate science behind the colors seen in the insect world.
Structural Coloration: The Iridescent Appearance
The striking, permanent purple and blue-violet coloration seen in certain bee species is not due to pigment. This effect, known as structural coloration, is the production of color by microscopic surface structures that interact with visible light. The bee’s cuticle, or exoskeleton, is intricately patterned with nanostructures instead of absorbing and reflecting wavelengths like a pigment.
These structures, which are often multi-layered, cause light waves to interfere with one another, scattering specific wavelengths like blue and violet. The result is iridescence, where the color changes depending on the angle from which the bee is viewed. This metallic sheen is a highly effective way for insects to achieve vivid colors. The underlying material is typically black, with the structural layers creating the shifting color on top.
The Pollen Effect: Temporary Purple Hues
A second, more common way for a bee to appear purple is by carrying purple pollen, which is a temporary effect. Bees collect pollen in specialized structures called scopae or pollen baskets (corbiculae). When a bee forages on a plant that produces naturally purple pollen, the collected load appears as a vibrant purple mass on the bee’s body.
Pollen is typically yellow, but certain plant species contain colored compounds that result in a purple shade. Plants known to produce deep purple pollen include:
- Phacelia tanacetifolia (Tansy-leaf Phacelia)
- Echium species
- Thistle varieties
- Fuchsia varieties
This coloration is often attributed to compounds like anthocyanins, which are also responsible for the color in blueberries and raspberries. The temporary purple color disappears once the pollen is deposited in the nest.
Specific Examples of Violet and Purple-Looking Bees
The most prominent example of a permanently purple-looking bee is the Violet Carpenter Bee, Xylocopa violacea, one of the largest bee species in Europe. This bee is easily recognized by its robust, black body and its shimmering, dark blue-violet wings. Its scientific name, violacea, directly refers to its striking coloration.
Other species within the Xylocopa genus, such as Xylocopa valga, also display a similar structural, iridescent blue-violet color. These bees are efficient pollinators, particularly of flowers with deep throats. Beyond the carpenter bees, various solitary bees like the Leafcutter Bees (Megachile species) can temporarily appear purple when their pollen-carrying hairs (scopa) are heavily loaded with dark pollen from plants like the American Bellflower (Campanula americana). This pollen-derived purple is a clear sign that the bee is actively foraging.