Likely European in origin this species now occurs throughout the world.
This species is closely related to Fannia canicularis, the Little House Fly, and has very similar habits. It is found worldwide and is often the more common of the two species. Adult males will hover for long periods, in a random back and forth manner, in shaded areas such as open garages, under patios or trees, etc. Females tend to rest on vegetation, and adult flies are attracted to nectar as well as honeydew from aphids, and may occur in large numbers near aphid-infested plants. Larvae feed within animal feces and often infest the accumulated materials in outhouses, thus their common name. They also infest pet droppings, bird feces, and even decomposing plant materials such as thick layers of mulch, piles of lawn clippings, and other damp resources.
The adult flies resemble House Flies, but are about half the size and with much thinner abdomens. The males have dark yellow patches on the sides of the abdomen, while the females are dark gray to shiny black. The wing vein patterns of the flies are distinctive, and on the flies of the genus Fannia the middle vein runs almost straight out to the tip, while on the House Fly that same vein has a 90 degree upward bend. The eggs and larvae of the Little House Fly are very different looking. The eggs are flattened and “veiny”, with flanges on each side that enable the eggs to float in very wet media. The larvae are covered with spiny projections along their top and sides, and turn from white to brown as they mature.
Characteristicts Important to Control:
Elimination of breeding sites for the larvae is extremely important, and in an urban setting this may be pet feces in yards, filthy garbage cans, or piled, decomposing lawn clippings. In rural areas the accumulation of livestock or poultry feces will produce vast numbers of flies. Proper exclusion from structures involves keeping doors and windows screened or closed, and the use of UV light traps will capture many adults indoors. Outdoors the use of fly bait strips or granules will be effective in killing adult flies. In locations where the adult males choose to hover continuously they can be discouraged by increasing the air movement through the area.