House flies (Musca domestica) do not possess the necessary mouthparts to bite or pierce human skin. This common confusion often stems from encounters with other types of flies that do bite.
The House Fly’s Non-Biting Mouthparts
House flies are equipped with a specialized feeding apparatus known as a proboscis, designed for sponging and lapping liquids, not biting. This flexible, tube-like structure has a spongy tip, the labellum, containing grooves that soak up liquid food.
House flies feed on dissolved sugars, decaying organic matter, and other moist substances. When encountering solid food, the house fly first regurgitates digestive enzymes onto the surface. These enzymes break down the solid material into a liquid, which the fly then absorbs.
This mechanism enables them to consume a wide range of food sources. Their mouthparts lack the rigid, piercing structures seen in biting insects.
What Attracts House Flies?
Since house flies do not consume blood, their presence near humans is driven by their search for food. They are primarily attracted to decaying organic matter, including rotting fruits, vegetables, and animal carcasses. Garbage, food waste, and animal feces also serve as significant attractants for these insects.
These environments provide the moist, fermenting substances that house flies require for feeding and laying their eggs. They play a role as scavengers in various ecosystems by helping to break down decaying organic material.
Flies That Do Bite Humans
The misconception that house flies bite often arises because people encounter other fly species that do possess biting mouthparts. One common culprit is the stable fly (Stomoxys calcitrans), which closely resembles the house fly but has a pointed, bayonet-like proboscis that protrudes forward from its head. Both male and female stable flies feed on blood and can deliver painful bites to humans and livestock.
Other biting flies include horse flies (Tabanus spp.) and deer flies (Chrysops spp.), which are typically larger and have powerful, scissor-like mouthparts for cutting skin and lapping up blood. Their bites are often quite painful and can result in welts. Mosquitoes (Culicidae) are also well-known for their biting habits, using a needle-like proboscis to pierce skin and draw blood.
Health Risks Associated with House Flies
Though house flies do not bite, they can still pose health concerns due to their feeding habits and movement between unsanitary areas and human food sources. House flies can mechanically transmit various pathogens, including bacteria, viruses, and parasitic eggs.
They pick up these microorganisms on their legs, bodies, and mouthparts when they land on contaminated materials such as garbage, decaying matter, and feces. When a house fly subsequently lands on human food, utensils, or surfaces, it can transfer these pathogens, potentially contaminating them.
This mechanical transmission can lead to the spread of foodborne illnesses, such as salmonellosis and E. coli infections. They can also contribute to the spread of diseases like cholera and dysentery. Maintaining good hygiene and sanitation practices, such as proper waste disposal and covering food, helps to mitigate the risks associated with house flies.