Flies experience the world through a visual system distinct from that of humans. A fly’s compound eyes, unlike human eyes, consist of thousands of individual units called ommatidia. Each ommatidium acts as a separate light receptor, collectively forming a mosaic-like image. This unique structure grants flies an almost 360-degree field of vision but results in a low-resolution, blurry perception of their surroundings. Their visual acuity is significantly lower than ours, yet they excel at detecting motion, which is crucial for their survival. Understanding these differences helps explain why certain colors influence their behavior.
Colors Flies Avoid
Flies avoid certain colors, with research pointing to specific hues that repel them. Yellow consistently emerges as a color flies are less attracted to or actively avoid. This repellency is partly because flies struggle to differentiate yellow from white, a color they associate with open sky, offering little food or shelter. Warm tones like yellow and orange are generally less appealing.
Other colors also deter flies. Green, for instance, does not register vividly in the ultraviolet (UV) spectrum for many insects, making green objects less noticeable. Flies and other insects cannot perceive red; red objects are essentially invisible to them, making it a color they effectively avoid.
Flies possess a limited range of color perception compared to humans, typically having only two types of color receptor cells. This restricted vision makes it difficult for them to distinguish between certain shades. Their visual system is particularly sensitive to the UV spectrum, which influences how they perceive different wavelengths of light.
Colors Flies Are Attracted To
Flies are strongly drawn to specific hues, with blue being a prominent attractant. Research indicates that flies are significantly more attracted to blue than to yellow. Blue is frequently used in commercial fly traps to lure these insects. The appeal of blue may stem from its balance of ultraviolet wavelengths and shadow, making it highly visible and stimulating.
Darker colors, including black, also attract flies. These surfaces absorb heat and create visual contrasts mimicking environments flies seek for shelter, food, or breeding grounds. Flies are also drawn to a mix of UV light and black shadows, as UV light strongly attracts many flying insects.
Flies may also be attracted to blue, mistaking it for animals (a food source for biting flies) or shady resting areas. The intensity of blue light might simply make it more stimulating.
Putting Knowledge Into Practice
Understanding fly color preferences offers practical approaches for deterring them. To reduce fly presence, use yellow light bulbs, as studies show yellow light is less attractive to flies. Painting outdoor surfaces with warmer tones like yellow can create an environment less appealing to flies.
For personal use, selecting clothing in warm tones like yellows or light oranges may reduce flies landing on you. Conversely, in areas with biting flies, avoid wearing blue due to its strong attractive qualities. For exterior home painting, colors like light gray, light blue, mint green, or pale yellow can deter various insects, including flies. Neutral tones like beige or cream are generally less appealing to pests.
When using fly traps, which often employ blue light due to its strong attractive properties, strategic placement is important. These traps should be positioned far from areas you wish to keep fly-free, drawing insects away from your immediate vicinity.