STABLE FLY
Identification, Facts, & Control
Latin Name
Stomoxys calcitrans
Appearance
abdomen is marked with circular spots
The stable fly is another fly which is often casually mistaken for the house fly. Despite its name, the
stable fly is actually much less common around stables than is the house fly. The upper surface of the stable
fly’s abdomen is marked with a number of dark, circular spots not found on the house fly. When at rest, the
wings of the stable fly are held widely spaced apart whereas the house fly rests with its wings projected
backward.
From an economic standpoint, perhaps the most important difference between the stable fly and house
fly is that the stable fly has piercing—sucking mouthparts and is a vicious "biter" opposed to the lapping-
sponging mouthparts of the house fly which cannot bite. Stable flies occur primarily outdoors and are daytime
biting flies. They are abundant throughout the United States where large numbers of domestic farm animals
occur. The stable fly prefers left—over, moist, decaying hay, alfalfa or grain found beneath the outdoor feed
racks of cattle feed lots and these materials must remain moist in order for the larvae to survive. The floor of the
stalls of horse stables are usually covered with fresh straw periodically and as the horse in an individual stall
urinates and deposits its droppings on the straw and in the course of the day, tramples straw, manure and urine
together, a layer of material that is highly nutritional for the stable fly larvae is produced. Adult stable flies lay
enormous numbers of eggs in this ready-made larval smorgasbord and the result is the existence of literally
sheets of thousands of fly larvae just under the top layer of straw. Anyone with a pitchfork can reveal this most
impressive sight. The bottom layer of old straw piles that are left in fields may also harbor stable fly larvae,
particularly if cattle have access to the straw and moisten it with urine. Still other places where stable flies may
breed are in decaying piles of weeds, lawn clippings and piles of waste vegetables or in excrement if it is mixed
with decaying vegetable matter. Stable flies may also occur along beach areas where they can breed in the
fermented marine vegetation (seaweed) that is deposited above the normal high tide mark.
As livestock pests, stable flies are extremely annoying. Mass attacks on livestock can cause loss of
blood, flesh, lowered milk production and reduced vitality thus making the animals susceptible to disease as
well as, causing tissue and hide damage. As a human pest, the bite of the stable fly can be quite painful. Stable
flies can be a major nuisance on warm summer evenings to people enjoying their backyard patios. On the
Atlantic and Gulf coasts as well as, along large inland lakes and rivers, stable flies can make beach areas unfit
for recreational uses in late summer.
Stable flies usually bite at the ankle level and draw blood quickly from their victims and feed to full
capacity in three to four minutes if left undisturbed. Beth sexes bite and suck bleed.
The stable fly larva requires six to twenty—six days to develop under normal summer breeding
conditions. Prior to pupating, the larvae crawl to the drier parts of their breeding medium.
The pupae are brown in color and may sometimes be found in enormous numbers. The pupal period
lasts five to twenty six days. Temperature and moisture conditions greatly influence developmental rates. The
adult fly lives about one month. Stable flies are able to fly for several miles.
Click on a species of flies below to learn further information.