What colors are biting flies attracted to? An expert guide

September 22, 2025 •

4 min read

According to a 2023 study published in Proceedings of the Royal Society B, day-biting flies are strongly attracted to blue objects, often mistaking them for potential hosts. Understanding what colors are biting flies attracted to is crucial for anyone hoping to avoid painful bites and discomfort outdoors.

Quick Summary

Biting flies are most attracted to blue and other dark colors, including black, brown, and red, as these colors absorb heat and create a strong silhouette that resembles large mammals. Light, cool-toned colors are generally less appealing to them.

Key Points

Blue Is a Strong Attractant: Studies show that many day-biting flies, including tsetse and horse flies, are particularly drawn to blue objects, mistaking them for animal hosts.
Dark Colors Create a Target: Dark shades like black and deep brown absorb heat and create a prominent silhouette, both of which attract biting insects.
White and Light Colors Repel: Wearing light-colored clothing, especially white and pastels, makes you less visible and thermally appealing to biting flies.
Use Traps Strategically: The attraction to blue and black is utilized in commercial fly traps, which can be placed strategically to divert flies away from you.
Clothing is Your First Defense: The most effective way to prevent bites is to wear long-sleeved, loose-fitting, light-colored clothing that covers exposed skin.
Attraction Varies by Insect: While blue attracts biting flies, mosquitoes are more drawn to dark, red-orange tones and ignore blue and green, highlighting species-specific visual preferences.

The Science Behind Fly Color Attraction

Research into insect vision reveals that biting flies, such as horseflies, tsetse flies, and stable flies, perceive colors differently from humans. Their attraction is not random but based on evolved visual systems that help them locate hosts for a blood meal. For many years, scientists observed that blue objects were particularly effective for traps, but a 2023 study shed light on the 'why'. By using artificial neural networks to mimic fly vision, researchers found that the flies' visual systems process blue and green light in an opponent manner, causing them to misclassify blue objects as animals against a green foliage background.

Why blue and dark colors are magnetic

Beyond the specific blue-green color processing, biting flies are drawn to dark objects for several reasons:

Resembling a host: Darker colors mimic the coloration of large mammals that are primary food sources for these insects, such as horses, cattle, and deer. This visual cue helps them find a blood meal effectively.
Heat absorption: Dark surfaces absorb more light and heat, creating a warm thermal signature. Since biting flies are attracted to body heat, they can be drawn to dark-colored clothing or objects that are warmer than their surroundings.
Enhanced silhouette: Dark clothes create a more distinct silhouette against a lighter background. This contrast makes it easier for biting flies to spot and track a potential host from a distance.

Which colors repel biting flies?

If you want to avoid attracting biting flies, the opposite of the above principles holds true. Light colors are your best bet for blending in and reducing your visual and thermal footprint.

Here are the colors that are less attractive to biting flies:

White: Reflects most light and heat, making you less visible and less thermally detectable to flies. Some species, like black flies, find white clothing significantly less attractive.
Light Green and Yellow: While some insects, like bees, are drawn to yellow, many biting flies find light green and other pastels less appealing than dark colors.
Pale Blue: Lighter shades of blue are less attractive than the darker, more intense blues used in commercial fly traps.

Practical applications for outdoor activities

Knowing how biting flies perceive color can directly impact your strategy for avoiding bites. From choosing your outfit to setting up pest control, these visual insights are highly effective.

How to choose your clothing

When heading outdoors, selecting the right attire can significantly reduce your chances of being targeted by biting flies.

Wear light colors: Opt for light-colored, neutral clothing like white, beige, khaki, or light gray. These colors reflect light and heat, making you less conspicuous.
Cover up: Choose long-sleeved shirts and long pants to cover as much skin as possible. This provides a physical barrier and minimizes exposed areas.
Opt for loose-fitting clothes: Loose-fitting clothing can make it harder for flies to access your skin and bite through the fabric. It also improves air circulation, helping you stay cooler and less appealing.
Tuck it in: Tuck your shirt into your pants and your pants into your socks or high boots. This prevents flies from crawling underneath your clothes to reach your skin.

Designing effective fly traps

The science of color attraction is actively used in pest management. Commercially available traps often employ a combination of visual cues to maximize their effectiveness. Many use blue panels or black stripes to attract flies, and then capture them on a sticky surface or with a pesticide.

Comparison of color attraction and repulsion

To put it all into perspective, here is a table comparing the attractiveness and repellency of various colors to biting flies and other common insects. The information helps illustrate the nuance required when using color as a defense strategy.


Color	Attracts Biting Flies	Repels Biting Flies	Other Insect Attraction	Notes
Blue (dark)	Yes	No	No	Strong attractant for tsetse and horse flies.
Black	Yes	No	Mosquitoes	Absorbent of heat, creating a strong silhouette.
Dark Brown/Red	Yes	No	Mosquitoes	Also mimics large mammal coloration and absorbs heat.
White	No	Yes	Low overall	Highly reflective, reduces visual and thermal signature.
Light Green	No	Yes	Low overall	Blends into foliage, less attractive than darker tones.
Yellow	No	Yes (most)	Pollinators, some plant pests	Repels biting flies, but can attract beneficial and other nuisance insects.

Conclusion

The visual world of biting flies is a crucial factor in their host-seeking behavior. They are disproportionately attracted to blue and other dark colors because these shades mimic the appearance and thermal properties of their natural animal hosts. By intentionally wearing light-colored, loose-fitting clothing that covers your skin, you can significantly reduce your chances of being targeted. Furthermore, incorporating blue and black traps in strategic outdoor locations can be an effective part of a comprehensive pest management plan. For more in-depth information on the research, explore the Journal of Medical Entomology and other entomology sources. Understanding this aspect of insect behavior is a simple but powerful tool for enhancing your safety and comfort outdoors.

Frequently Asked Questions

To avoid biting flies, you should wear light-colored clothing, including white, khaki, or pastels. These colors are less attractive to flies and reflect heat, making you less of a target.

Biting flies are highly attracted to blue, especially dark blue, but are typically repelled by green. They distinguish between the two via an opponent process in their visual system, which helps them identify potential hosts (like animals) against a background of foliage (green leaves).

While many diurnal biting flies share an attraction to blue and dark tones, specific preferences can vary. For example, some mosquito research indicates they are drawn to red and orange, in addition to dark colors, but tend to ignore blue and green.

Biting flies are attracted to dark colors because these shades absorb heat and create a strong, visible silhouette against a lighter background. Both thermal signatures and visual outlines are used by flies to locate potential blood meal hosts.

The attraction is linked to how flies' visual systems process color. In the case of blue, it is believed they mistake the color for a potential animal host during a blue-green photoreceptor opponency process. For dark colors, it is a combination of heat absorption and a visible silhouette.

Yes, color is only one attractant. Biting flies are also drawn to hosts by sensing carbon dioxide (exhaled breath), warmth, perspiration, and certain body odors.

Yes, but with caution. Light, bright colors like white, light gray, and light green are less attractive to biting flies. However, bright yellow can attract other insects like pollinators.