House flies are common insects that leave small spots on household surfaces due to their unique feeding behavior. Lacking the necessary mouthparts to chew solid food, a fly must liquefy its meal externally before ingestion. This process involves the fly regurgitating a mixture of digestive enzymes and saliva onto a food source to break it down into a consumable liquid. The resulting spots, which are essentially fly vomit, are frequently mistaken for other types of insect waste.
Identifying Fly Regurgitation Marks
Regurgitation marks are often deposited on surfaces like countertops, windowsills, and food. These spots are typically small, circular, and measure approximately one to two millimeters in diameter. When fresh, the marks may appear moist or sticky, but they quickly dry into a crusty residue on the surface. The color varies significantly depending on what the fly has recently consumed, ranging from pale, yellowish, or creamy white (from sugary liquids) to brownish or dark (from organic matter or blood).
How Fly Vomit Differs From Fly Feces
The primary difference between fly vomit and fly feces, commonly called flyspeck, lies in their biological purpose and physical appearance. Fly vomit is associated with external digestion and is generally a slightly larger, more diffuse, and circular mark. It represents an active step in the fly’s feeding process. Fly feces, on the other hand, are the true waste product of the fly’s rapid digestive system, appearing as consistently much smaller and darker dots. Feces often have a distinct, slightly elongated or tear-drop shape, sometimes described as having a small tail.
Health Concerns and Immediate Cleaning Procedures
The presence of fly regurgitation is a public health concern because it is a primary way that flies transmit disease-causing pathogens. A fly picks up bacteria like Salmonella, E. coli, and various viruses from unsanitary material, such as decaying waste or feces. When the fly regurgitates onto a clean surface, it effectively transfers these harmful microorganisms. This mechanical transmission poses a direct risk of foodborne illness, especially if contamination is on food preparation areas or uncovered meals. Exposed food suspected of contamination must be discarded immediately.
The cleaning of contaminated surfaces must be a two-step process to ensure proper sanitation. First, the visible residue should be removed by gently washing the area with hot, soapy water to lift the organic material. This initial step cleans the surface but does not fully disinfect it. Next, the surface must be disinfected to neutralize any lingering pathogens. A solution of one part household bleach to ten parts water, or an equivalent EPA-registered disinfectant, should be applied and allowed to remain wet on the surface for at least five minutes before being wiped dry.
Preventing Future Fly Contamination
The most effective way to address fly contamination is by focusing on proactive exclusion and stringent sanitation methods. Since flies are attracted by odors and the presence of organic matter, eliminating their access to food and breeding sites is paramount. Physical controls, such as sticky traps or non-chemical UV light traps, can be used to capture adult flies that do manage to enter the space.
- Ensure all exterior doors and windows have tightly fitted, intact screens, and repair any tears or gaps immediately.
- Dispose of all food waste promptly in trash receptacles that have tight-fitting lids.
- Practice immediate cleanup of food spills inside the home.
- Consistently store all food, including pet food, in sealed containers.