Drain flies, also known as moth flies or sewer gnats, are small insects commonly found in homes and commercial buildings. Their presence often sparks questions about their behavior, particularly regarding light. While a common belief suggests a strong attraction to light, understanding their true habits reveals a more complex interaction with their environment.
Drain Flies and Light
Drain flies are not strongly attracted to light like many other insects, such as moths. They are weak fliers, making short, hopping movements rather than sustained flights toward a light source. While they often rest on walls or ceilings during the day, some observations show they may congregate around light sources like lampshades or windows at night. However, this attraction is not their primary orienting behavior. Unlike highly phototactic insects, light traps are ineffective for eliminating an infestation because they do not address the underlying breeding source.
What Really Attracts Drain Flies
The primary attractant for drain flies is moist, decaying organic matter, which serves as both a food source and a breeding ground. These insects thrive in environments containing a gelatinous film or sludge, often found lining the inside of drains and pipes. This organic accumulation, composed of hair, soap scum, food particles, and other debris, provides the sustenance their larvae require to develop. Drain flies are also drawn to standing water and consistently wet areas, including infrequently used drains, leaky pipes, dirty trash cans, and overwatered potted plants. These conditions indicate a suitable habitat for their entire life cycle.
Strategies for Drain Fly Elimination
Effective drain fly elimination focuses on removing their breeding grounds and food sources, not just targeting adult flies. A primary step is thoroughly cleaning drains by physically removing organic sludge. Using a stiff brush or drain snake can dislodge the film lining pipes, followed by hot water, baking soda, and vinegar to further clean the area. Addressing any sources of standing water or excessive moisture is also important, such as fixing leaky pipes or ensuring proper drainage. Regular maintenance, including routine drain cleaning and good ventilation, helps prevent future organic matter accumulation. Light traps or aerosol insecticides alone will not resolve an infestation, as these methods only address adult flies and fail to eliminate the source.