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What Are Filth Flies?

The common house fly regurgitates its stomach contents onto its food to liquify it. It then re-ingests the stomach contents along with whatever food it is eating --- be it dung, garbage or the contents of your picnic basket. This is only one of the behaviors that have earned the house fly its place among the two-winged insects known as filth flies. It is far from the only, or even the worst, on the list.

Flies
- True flies have two wings, one on each side, and are of the order Diptera, which means "two wing." Each group of flies goes through four stages of life: egg, larva, pupa and adult. Most familiar by sight to many are the fly larva, otherwise known as maggots, and adult flies. Maggots are hatched from eggs laid in organic material that is in a state of decay such as garbage, sewage or dead mammals.
Big Filth Flies
- The blow fly is also known as a bottle fly because of its shiny, blue covering.
  
  House flies are considered one of the larger filth flies. Also in this group are blow, flesh and stable flies. Each type has its favorite, though not exclusive, type of area for feeding and breeding and is named accordingly. House flies are attracted to moist, rotted garbage or things with strong smells, such as pet feces. The shiny blue and green blow fly prefers to lay its eggs in the rotting carcasses of dead animals. A number of these seen in or around your home could indicate that a mouse or some other animal has expired between the walls of the house. Flesh flies lay their eggs in carrion but will also lay them on scraps of meat. Stable flies feed on animal and human blood and lay their eggs in piles of manure, rotting straw or wet or rotting feed.
Small Filth Flies
- Fruit flies look at a rotting apple core and see a perfect home for their eggs.
  
  The minute fruit flies you see hovering around ripe or rotting fruit are considered filth flies. This is where they prefer to lay their eggs, though they are also attracted to vinegar, soda and other sweet or fermented material. Drain fly larva live and grow in the muck that gathers in kitchen and bathroom drains and use breathing tubes to gain access to air. The adult flies often crawl out of the drains. Fungus gnats are, as their name indicates, attracted to fungus and can be seen around pigeon droppings or at the base of over-watered plants. Phorid flies, attracted to carrion and other decomposing plant or animal material, can quickly grow into a large infestation.
Prevention and Control
- Sanitation is the best way to prevent an infestation of filth flies. Identify the fly and its source of attraction. Eliminate their food sources, and breeding sites and you remove the source of their attraction. Keep garbage in sealed containers or plastic bags; keep Dumpsters as far from a building as possible; put screens in all windows and doors.

Insects & Science