Stable Fly
Stomoxys calcitrans (Linnaeus), Muscidae, DIPTERA


Adult -- The stable fly resembles the house fly but is more robust and aggressive and inflicts an irritating bite. About 6 or 8 mm long, it has 4 distinct, dark longitudinal stripes on the thorax and several dark spots on the abdomen with sharp mouthparts protruding from the head.

Egg -- The egg is about 1 mm long and creamy white. It is curved on one side and straight and grooved on the other.

Larva -- About 1.25 mm long, the young larva is translucent and difficult to see. It grows rapidly; the mature larva is about 11 to 12 mm long and pale yellow to creamy white in color.

Pupa -- The full grown larval skin hardens to form the pupal case (puparium) in which the pupa develops. The puparium is soft and yellowish at first, but it soon becomes hard and reddish-brown. It is 4.25 to 6 mm long and wider at the head end.


Distribution -- Stable flies are worldwide pests of livestock and man. Reported in the United States as early as 1912, these flies are now found throughout North America and are often numerous throughout North Carolina.

Hosts -- Cattle, horses, hogs, mules, dogs, cats, and man are attacked by stable flies.

Damage -- Stable flies are nuisance flies which inflict irritating bites. They can, when numerous, weaken livestock by their blood sucking activities. They also interrupt cattle's normal feeding and resting activities, which in turn reduces weight and milk production. Besides being vicious biters, stable flies may transmit animal diseases such as hog cholera.

Life History -- Eggs are deposited in wet, organic materials such as straw, litter, manure mixed with straw or other bedding, vegetable or fruit matter, marine grasses on shore, grass clippings, waste silage or feed in feedlots or compost heaps. However, manure piles are not favorable breeding sites. The female deposits 35 to 80 eggs at one time deep in the material, often in pairs or small clusters. Ten or 11 egg-laying periods occur during the life of the fly (4 to 6 weeks).

The eggs hatch in 1 to 3 days, and the young larvae (maggots) immediately begin to feed, completing development in 14 to 26 days. As in the house fly life cycle, the third-stage larvae seek drier environments for pupation, which lasts 5 to 26 days. Within an hour after emerging, the adult can fly, and it is ready to feed and mate soon afterwards. Females usually begin laying eggs 5 to 10 days after emergence. Total time of development from egg to adult averages from 21 to 25 days and several generations occur each year. Stable flies usually overwinter as larvae and pupae, but in the southern states the adult flies are often active during warm periods throughout the winter.

Feeding requires 2 to 5 minutes, but since the flies are easily disturbed, several "bites" may be necessary to complete one feeding. After the mating, at least 3 complete feedings are required before egg laying can occur. Stable flies are capable of long flights in search of a blood meal.


The most effective method of stable fly control is scattering of the breeding material. Scattered, it will dry rapidly and deny the flies a moist breeding site. Insecticide treatment provides protection to the cattle but offers only temporary control because the flies do not remain on the animals after feeding.