The common house fly, Musca domestica, is a ubiquitous insect found globally. These small, two-winged creatures, typically 6 to 7 mm long, are a familiar sight, frequently landing on people and surfaces. This behavior stems from their biological needs and sensory capabilities.
What Attracts Flies to Humans
Flies are drawn to humans by sensory cues signaling potential food sources. They possess an acute sense of smell, detecting odors like carbon dioxide exhaled during breathing, as well as lactic acid and carboxylic acids present in human sweat and skin oils. Body heat also serves as an attractant, guiding flies toward warm surfaces.
Flies seek specific nutrients on human skin. They are interested in sweat, which contains proteins, carbohydrates, salts, and sugars. Dead skin cells and bacterial growth associated with sweat provide further sustenance.
Their Behavior on Your Skin
Once a fly lands on human skin, its actions are driven by its feeding mechanism. Flies “taste” with their feet, using chemoreceptors on their tarsi to determine if a surface is a viable food source. If the surface contains desirable nutrients, the fly will prepare to consume them.
Since flies lack chewing mouthparts, they must liquefy solid food before ingestion. They achieve this by regurgitating digestive fluids onto the surface. These enzymes break down material, allowing the fly to then suck up the resulting liquid with its sponge-like proboscis. Flies also defecate frequently, depositing small, dark specks wherever they land.
Potential Health Risks
Flies pose health risks because they frequent unsanitary environments, such as decaying organic matter, feces, and garbage, where they pick up various pathogens. Over 100 different pathogens have been associated with house flies. When a fly lands on human skin, it can mechanically transfer these microorganisms.
Flies can transmit diseases like E. coli, Salmonella, and food poisoning, as well as more severe conditions such as typhoid and cholera. While the risk from a single fly landing may be low, it exists, especially when flies land on open wounds or food that is subsequently consumed.
Keeping Flies Away
Minimizing fly presence involves reducing attractants and blocking access. Maintaining personal hygiene, such as promptly cleaning sweat and oils from the skin, can make individuals less appealing to flies.
Around the home, preventing flies begins with cleanliness and proper waste management. Food should be kept covered, and spills should be cleaned immediately. Regularly emptying and cleaning garbage cans, ensuring they have tight-fitting lids, and disposing of pet waste promptly are important steps. Installing screens on windows and doors can prevent flies from entering indoor spaces. Natural repellents, such as essential oils like lavender, peppermint, eucalyptus, or lemongrass, can also deter flies.