Flies are a common nuisance, often found buzzing around homes and outdoor spaces. Understanding their response to light offers effective strategies for managing their presence. Certain light colors can influence fly behavior, providing a method for deterring them from unwanted areas.
Colors That Repel Flies
Flies generally avoid light in the yellow, orange, and red spectrums. These colors, characterized by longer wavelengths, are less visible or stimulating to flies. Yellow light can reduce the attraction of flies. While yellow light bulbs don’t actively repel flies, they are less attractive to them than other colors.
Red light is even less attractive to flies, as many cannot perceive this color at all. This is because red light falls into the lowest frequency range visible to humans, and flies’ visual systems are not well-tuned to these longer wavelengths. Utilizing light sources that emit primarily in these warmer hues can make an area less appealing to flies.
How Flies Perceive Light
Flies possess compound eyes, which are vastly different from human eyes. These eyes consist of thousands of tiny units called ommatidia, each acting like a miniature eye that captures light and sends it to the fly’s brain, creating a mosaic-like image. Unlike humans, who perceive a broad visible spectrum, flies can see a wider range of light, including ultraviolet (UV) light, which is invisible to the human eye.
Their photoreceptor cells are particularly sensitive to UV, blue, and green light wavelengths. Conversely, flies are less sensitive to longer wavelengths, such as those found in yellow, orange, and red light. This difference in spectral sensitivity explains why these warmer colors are less appealing to flies; they do not register as vividly or are perceived as “darker” by their visual system.
Using Light to Deter Flies
To deter flies, consider installing yellow-hued outdoor lighting. Specialized “bug lights” or LED bulbs designed to emit light primarily in the yellow or amber spectrum are effective choices. These lights reduce fly attraction while still providing sufficient illumination for humans.
Strategic placement is important; positioning them away from gathering areas, such as patios or doorways, can limit fly presence. While yellow lights are beneficial, they are not a complete solution on their own. Light-based deterrence is most effective when integrated into a broader fly control strategy, which might include sanitation and other repellent methods.
Colors That Attract Flies
Conversely, flies are strongly drawn to light in the blue, green, and ultraviolet (UV) ranges. This attraction is exploited in many commercial insect traps, which often emit UV light to lure flies. Flies are attracted to UV light because it mimics natural reflective properties of food sources like flowers, fruits, or decaying organic matter.
Blue light also acts as a strong visual attractant for flies, outperforming other hues in studies. Flies perceive blue light as highly visible and stimulating due to its balance of ultraviolet wavelengths and shadow. This natural preference for blue can lead flies towards areas illuminated by such light, making them more prone to congregating in those spaces.