Many fly species consume feces, a behavior that plays a natural role in the decomposition of organic matter. This activity allows them to acquire essential nutrients and contribute to environmental recycling. While this feeding habit is natural for flies, it carries implications for human health due to the environments they frequent.
Why Flies Seek Out Feces
Flies are attracted to feces and other decaying organic materials because these substances serve as rich sources of nutrients and provide suitable environments for reproduction. Feces contain a variety of lipids, proteins, carbohydrates, and minerals, all necessary for fly survival, egg production, and larval development.
Flies, particularly their larval stages known as maggots, are significant decomposers. They consume and break down dead organic matter, including feces, which prevents accumulation and releases nutrients back into the environment. This process is crucial for nutrient cycling, enriching the soil and supporting plant growth. The attraction to these materials is an evolved behavior that allows flies to exploit readily available resources that other organisms might not utilize.
How Flies Feed on Organic Matter
Flies possess unique mouthparts adapted for consuming liquid or semi-liquid substances. The house fly, for instance, has sponge-like mouthparts called a labellum. When encountering solid or semi-solid food like feces, the fly regurgitates a mixture of saliva and digestive enzymes onto the substance, liquefying it externally.
Once the food is liquefied, the fly sops up the nutrient-rich fluid using its labellum. The regurgitation and re-ingestion process is a key aspect of their feeding mechanism, enabling them to consume a wide range of decaying organic matter.
Health Risks Associated with Fly Feeding
The primary health risk associated with flies feeding on feces stems from their role as vectors for pathogens. As flies land on and consume contaminated materials like feces, they pick up bacteria, viruses, and parasites on their bodies. These pathogens can then be transferred to human food, kitchen surfaces, and even directly to people when the fly lands elsewhere.
Flies can mechanically transmit over 65 different diseases. Common examples of pathogens they can spread include E. coli, Salmonella, and Shigella. They are also known to transmit serious illnesses such as typhoid fever, cholera, and anthrax. Beyond external contamination, flies can also defecate and regurgitate on food, directly introducing microbes from their digestive tracts onto human consumables. To reduce these risks, covering food and maintaining high standards of hygiene are important preventive measures.