Flies often buzz close to humans, a common source of irritation. Understanding the science behind this behavior explains why these insects are drawn to our presence.
What Attracts Flies to People
Flies possess highly sensitive sensory organs that detect a variety of chemical and physical cues emanating from humans. Our bodies release volatile organic compounds through sweat and skin oils, which serve as strong attractants for many fly species. These compounds signal the presence of moisture and nutrients, drawing flies in to investigate potential food sources.
Humans exhale carbon dioxide, a gas flies detect from a considerable distance. This carbon dioxide plume acts as a beacon, indicating the presence of a large, living organism that could represent a food source or a warm resting spot, guiding flies toward their target.
Flies are drawn to the warmth generated by the human body. Body heat signals a suitable environment for some fly species, particularly those that seek out warm-blooded hosts or prefer warmer temperatures for activity. Even microscopic traces of food, sugary drinks, or other organic residues on skin or clothing can attract flies. These tiny particles provide a direct source of nutrients, and flies are highly adept at locating them.
How Flies Navigate and Respond
Flies navigate their environment using their compound eyes, which provide a nearly 360-degree field of vision. This wide perspective, combined with their ability to process visual information rapidly, allows them to detect even slight movements and maintain awareness of their surroundings. Their erratic flight patterns, often appearing as circling, are part of this continuous visual scanning.
The seemingly aimless circling behavior is actually a form of exploratory investigation. Flies are constantly searching for food, mates, and suitable locations to lay eggs. When they encounter a human, they will often circle to assess the potential for any of these resources, using their highly developed senses to gather more information from different angles.
After this initial circling, a fly may attempt to land on the skin or clothing to investigate further. They use specialized chemoreceptors on their legs to “taste” surfaces, identifying any available sugars, salts, or other organic compounds. This probing behavior is a direct result of their search for sustenance. When a human makes a sudden movement, the fly’s rapid visual processing allows it to dart away quickly, but the initial attractants often cause it to return to the vicinity shortly after.
Keeping Flies Away
Maintaining personal hygiene can significantly reduce the attractiveness of humans to flies. Regularly showering and wearing clean clothes minimizes the accumulation of body odors and sweat that release volatile organic compounds. Reducing these sensory cues can make a person less appealing to flies seeking moisture or nutrients.
Ensuring environmental cleanliness is important for deterring flies around living spaces. Promptly cleaning up food crumbs, drink spills, and securing trash in sealed containers removes accessible food sources that would otherwise draw flies indoors. This eliminates the primary reason flies enter human dwellings.
Using physical barriers prevents flies from entering indoor areas. Installing screens on windows and doors blocks their entry while allowing ventilation. Creating air currents with fans also deters flies, as their small bodies struggle to fly effectively against even a gentle breeze. Some insect repellents, including those with natural ingredients like essential oils, can deter flies from approaching.