The stable fly, Stomoxys calcitrans, is often called the biting house fly. It is about the same in size and general appearance as Musca domestica, the house fly. It is brownish gray, the outer of four thoracic stripes is broken, and the abdomen has a checkered appearance. The stable fly has a bayonet-like, needle-sharp proboscis that, when at rest, protrudes forward from the head. The wings, when at rest, are widely spread at the tips. These flies are found throughout the world. In the US, they are found in the midwestern and southeastern states. (See .)
Stomoxys calcitrans (stable fly), a biting fly of veterinary importance that sucks blood from mammals.
Courtesy of ABOL/HP Fuehrer Vetmeduni Vienna.
The stable fly is often prevalent in summer. Adult flies rest on vertical surfaces such as fence posts and railings. Larval and pupal forms develop in decaying organic matter, including grass clippings and seaweed along beaches. In the midwestern US, larvae can be found in wet areas around the edges of haystacks and silage pits. When cattle are fed hay, breeding can occur at the edge of the feeding area where hay has become mixed with urine and feces. The life cycle in the field can be completed in 2–3 weeks. Female flies start to lay eggs 1 day after emergence and 5 days after a blood meal. Adults can live ≥ 3–4 weeks (1).
Pathology of Stable Flies
Both male and female stable flies are avid blood feeders, staying on the host for short periods of time, during which they obtain blood meals. Flies feed on blood 1–3 times a day, each time sucking approximately 0.02 mL of blood. Each feeding session takes only 2–5 minutes, after which flies leave the host to rest on a nearby surface (1). These are outdoor flies; however, in the late autumn and during rainy weather, they might enter barns.
Stable flies bite and feed on any warm-blooded animal. If an animal has more then 20 stable flies biting it at once, the animal's ability to feed and care for itself is impacted, with measurable effects on weight gain and condition (2). In dairy cattle, animals with more than 50 flies will have milk production decrease by 40–60% (1).
Horses and cattle are the preferred hosts for the stable fly. The fly usually lands on the host with its head and proboscis pointed upward and inflicts painful bites that puncture the skin and bleed freely. It is a sedentary fly, not moving on the host. Stable flies usually attack the legs and ventral abdomen and might also bite the ears. They can be a problem in cattle feedlots in the midwestern US. The damage inflicted on cattle is due to the painful bites and blood loss, and the irritation results in decreased efficiency in converting feed to meat or milk.
In small animals (eg, dogs), stable flies prefer to feed on the ear tips of dogs with pointed ears, especially German Shepherd Dogs.
Stable flies are mechanical vectors for the causative agents of anthrax (Bacillus anthracis), surra (Trypanosoma evansi), and equine infectious anemia (equine infectious anemia virus). They are the intermediate host for Habronema muscae, a nematode found in the stomach of horses.
Diagnosis of Stable Flies
Stable flies are easily identified by their size (approximately that of the house fly), coloration, and bayonet-like proboscis that protrudes forward from the head. Affected animals will try to avoid swarming flies by stamping their feet, swishing their tails, tossing their heads, and kicking sand up onto their legs and bodies.
Treatment and Control of Stable Flies
Sanitation
The main consideration in stable fly control is sanitation, which can effect up to 90% control (3). Areas along fencerows, under feed bunks, and wherever feces and straw or decaying matter can accumulate should be kept clean, because these substrates provide the medium in which the larval flies develop. If good sanitation procedures are practiced, chemical control is less likely to be needed.
Stable fly burdens of approximately three flies per leg can decrease cattle weight gain by approximately 0.2 kg/day, highlighting the economic value of effective fly control (4). Stable flies feed on the lower portions of cattle, around the legs and belly, including the udder. They usually feed only once or twice daily for short periods, thus minimizing exposure to compounds applied to these areas. For cattle in pasture systems, insecticide application remains the most practical and effective method of stable fly control. Most on-animal products are synthetic pyrethroids, primarily deltamethrin zeta-cypermethrin, which provide both insecticidal and repellent activity. However, reliance on pyrethroids increases the risk of insecticide resistance, and stable fly resistance has been reported in the US and Brazil (5, 6).
Alternative approaches include biorational repellents, such as plant-derived essential oils and fatty acid–based formulations that have known activity against stable flies and can contribute to insecticide resistance management programs. Attract-and-kill technologies have been developed, using visually attractive traps coated with adhesive and supplemented with host-associated odor attractants, such as m-cresol and p-cresol. Push-pull strategies combine on-animal repellents (the "push") with odor-baited traps (the "pull") to decrease stable fly pressure on grazing livestock (7). These integrated approaches offer promising alternatives or complements to conventional insecticide-based control.
Topical pyrethroid-based repellents used in dogs might also decrease exposure to other biting flies; however, efficacy can vary among species and products.
For More Information
Stable fly. Department of Primary Industries and Regional Development. Government of Western Australia.
Also see pet owner content regarding flies and mosquitoes of dogs, cats, and horses.
References
Rochon K, Hogsette JA, Kaufman PE, Olafson PU, Swiger SL, Taylor DB. Stable fly (Diptera: Muscidae)—biology, management, and research needs, J Integr Pest Manag. 2021;12(1):38. doi:10.1093/jipm/pmab029
Taylor DB, Moon RD, Mark DR. Economic impact of stable flies (Diptera: Muscidae) on dairy and beef cattle production. J Med Entomol. 2012;49(1):198-209. doi:10.1603/me10050
Cook DF, Dadour IR, Voss SC. Management of stable fly and other nuisance flies breeding in rotting vegetable matter associated with horticultural crop production. Int J Pest Manag. 2011;57(4):315-320. doi:10.1080/09670874.2011.603063
Campbell JB, Skoda SR, Berkebile DR, et al. Effects of stable flies (Diptera: Muscidae) on weight gains of grazing yearling cattle. J Econ Entomol. 2001;94(3):780-783. doi:10.1603/0022-0493-94.3.780
Pitzer JB, Kaufman PE, Tenbroeck SH. Assessing permethrin resistance in the stable fly (Diptera: Muscidae) in Florida by using laboratory selections and field evaluations. J Econ Entomol. 2010;103(6):2258-2263, doi:10.1603/EC10166
Barros ATM, Rodrigues VD, Cançado PHD, Domingues LN. Resistance of the stable fly, Stomoxys calcitrans (Diptera: Muscidae), to cypermethrin in outbreak areas in Midwestern Brazil. Rev Bras Parasitol Vet. 2019;28(4):802-806. doi:10.1590/S1984-29612019089
Lehmann AT, Brewer GJ, Boxler DJ, et al. A push-pull strategy to suppress stable fly (Diptera: Muscidae) attacks on pasture cattle via a coconut oil fatty acid repellent formulation and traps with m-cresol lures. Pest Manag Sci. 2023;79(9):3050-3057. doi:10.1002/ps.7480
