All flies, and most other two-winged insect species belong to the Diptera order of insects, more than 100,000 of which are fly species. Although many fly species are well known pests that live in close association with humans, flies contribute significantly to the decomposition of dead organisms, making them ecologically important insects. Flies use dead and decaying organisms as breeding and egg-laying sites, and after larvae (maggots) hatch from their eggs, they consume the organic matter in order to obtain the nutrients they need to develop properly. The dead organisms that flies prefer for the purposes of breeding and egg-laying vary from species-to-species, but some of the most common include rotting food, garbage, compost, manure, dead plant matter, and animal carcasses. Flies are also the primary food source for many organisms, including fish, birds, snakes, spiders, and even carnivorous plants. Unfortunately, house flies, blow flies, fruit flies, phorid flies, drain flies and many other fly species are common house pests that breed on either indoor or outdoor sources of decaying organic matter.

Within homes, house flies and fruit flies prefer to breed on rotting food beneath appliances, in garbage receptacles, and in liquid residue in cans and bottles stored in recycle bins, but house flies are notable for readily breeding on a variety of dead organic materials. Naturally, maintaining well sanitized homes is key to preventing indoor fly pest issues, and it is worth noting that even tiny bits of food left behind on surfaces provides more than enough material for fly eggs of many species to develop into winged adults. The most important aspect of preventative fly control tactics is to promptly remove indoor garbage bags once they become full, and they should be tied tightly before being placed within a plastic outdoor garbage bin with a tight-fitting lid. Drain flies and phorid flies can lay thousands of eggs on the scum that collects in all indoor drains and pipes, and moisture in drains and pipes provide ideal breeding conditions for gnats. Because of this, drains should be regularly cleaned and water should be turned on at regular intervals to keep scum deposits from forming in pipes. Regularly flushing toilets within scarcely used guest bathrooms will keep P-traps full of water, making it impossible for drain flies or phorid flies to travel into homes from septic tanks.

Have you ever experienced issues with indoor flies that emerged from drains?