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Many of the most pestiferous and medically harmful airborne insects belong to the Diptera order. This insect order is comprised of 125,000 documented species, and experts believe that around 1 million additional Diptera insect species have yet to be discovered. Mosquitoes, flies and gnats are the most medically significant insect groups in the Diptera order, as mosquitoes are biological disease vectors, while flies transport dozens of disease-causing microorganisms to indoor surfaces and human foods.  Sylvicola fenestralis, or the “window gnat,” is a common home-invading and disease-spreading insect species that is often overlooked despite being a significant medical threat.

Adult window gnats are around 6 mm in length, and they closely resemble craneflies due to their noticeably long legs. Their spotted wings are dark brown, and females are known to inflict bites. Window gnats are frequently found in large numbers within homes, especially near windows, hence their common name. Much like flies, window gnats lay eggs on decaying sources of organic matter that larvae feed on after hatching. Unlike most fly species, window gnats lay eggs on many sources of organic matter, such as compost piles, fresh and rotting food, garbage, and sewer water. In fact, larvae are known for consuming the scummy film on the surface of sewer water where they acquire a number of pathogens. Due to their preference for sewage water and fresh foods, these pests frequently transport numerous pathogens to food items that have yet to be consumed. Because of this, the window gnat is one of the few Diptera species that has caused intestinal and urogenital myiasis. The latter disease is particularly unpleasant, as it involves larvae infesting the urinary tract. In homes and buildings, window gnat females lay 150 eggs at a time on food, garbage, and any moist surface.

Have you ever experienced an infestation of window gnats?