Stomoxys calcitrans

(Linnaeus, 1758)

Stable Fly, Barn Fly, Biting House Fly, Dog Fly, Power Mower Fly, Beach Fly, Lawn-mower Fly

Stomoxys calcitrans, commonly known as the , is a worldwide pest of livestock and humans. Both sexes are obligate blood-feeders, inflicting painful bites that cause significant economic losses in cattle operations through reduced weight gain and milk production. The is easily mistaken for the common house fly but distinguished by its . Native to Eurasia and Africa, it has spread globally through human activity.

Stomoxys calcitrans by (c) Bill Keim, some rights reserved (CC BY). Used under a CC-BY license.

Stomoxys calcitrans by (c) Judy Gallagher, some rights reserved (CC BY). Used under a CC-BY license.

Stomoxys calcitrans by (c) Conall, some rights reserved (CC BY). Used under a CC-BY license.

Pronunciation

How to pronounce Stomoxys calcitrans: /stɔˈmɔksɪs ˈkælsɪtrænz/

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

Distinguished from the house fly (Musca domestica) by the presence of a prominent black piercing projecting forward from under the ; house flies possess sponging mouthparts with a fleshy . Differs from horn flies (Haematobia irritans) in : stable flies rest on nearby surfaces after feeding rather than remaining continuously on the . Horn flies are also slightly smaller. Both sexes of stable flies bite, unlike many other blood-feeding flies where only females feed. The proboscis is visible even when folded, appearing as a slender black structure under the 'chin.'

Images

Appearance

stable flies measure 5-7 mm in length, similar in size to house flies. The body is predominantly gray with four dark longitudinal stripes on the . The most distinctive feature is the slender, black, slightly curved (beak) projecting forward from beneath the , used for piercing skin and sucking blood. When at rest, this proboscis is folded back under the head. The wings are clear with typical dipteran venation. Overall coloration and striping pattern closely resembles Musca domestica, contributing to frequent misidentification.

Habitat

Associated with confined livestock operations, farms, ranches, zoos, and coastal areas where large mammals congregate. Breeding sites require moist, decaying fibrous organic matter including: mixtures of manure and urine-soaked bedding, rotting hay or straw, silage, grass clippings, compost, partially composted livestock bedding, and algal masses. Unlike house flies, stable flies develop poorly in manure alone and prefer substrates with undigested plant material and higher protein content. Eurythermic capable of occupying diverse .

Distribution

Worldwide distribution; considered native to Eurasia and Africa. Introduced to the Americas, likely during colonial times possibly via ship's ballast. Now established across North America, South America, Europe, Asia, Africa, and oceanic islands. In the United States, particularly abundant in the Midwest and areas with intensive livestock production. In Mauritius, occurs throughout the island but less commonly than Stomoxys nigra in wetter high elevations; peak during cool, drier seasons.

Seasonality

fluctuate seasonally based on temperature and precipitation. In temperate regions, activity peaks during warmer months (May through October in Nebraska). In subtropical regions like Mauritius, populations increase during cool, drier seasons and decline during wet seasons. Year-round breeding possible in suitable conditions where substrates remain moist and temperatures permit development. live approximately 3 weeks under favorable conditions.

Diet

Obligate haematophagous; both males and females feed exclusively on blood. Blood meals obtained from mammals using . may also sip flower nectar for energy, but blood is required for .

Host Associations

Cattle - Primary Major pest of beef and dairy cattle; causes significant economic losses
Horses - Common ; horse manure preferred oviposition substrate
Humans - Incidental Bites readily when livestock unavailable; attracted to human breath and CO2
Other livestock - Sheep, goats, swine, and other domestic mammals

Life Cycle

Complete with four stages: , larva (maggot), pupa, and . Females deposit 25-50 eggs per batch, up to 600 eggs lifetime, singly or in clusters in suitable breeding substrate. Eggs hatch in 1-14 days depending on temperature. Larvae feed for 11-30 days (typically ~2 weeks), molting twice, reaching up to 12 mm before . Pupal stage lasts 6-20 days within a hardened capsule formed from the last larval . Total development from egg to adult averages 28 days but varies with temperature, humidity, and food quality. Multiple per year in favorable climates.

Behavior

blood-feeding activity with two feeding peaks per day at temperatures above 14°C. Both sexes bite aggressively and persistently, returning immediately after being disturbed. Unlike horn flies, stable flies do not remain on the ; they rest on nearby walls, fences, or vegetation between blood meals. Attracted to hosts by carbon dioxide, body heat, movement, and specific volatile compounds including dimethyl trisulfide, butanoic acid, p-cresol, and octenol. Can locate oviposition sites using olfactory cues alone, showing strong preference for horse manure over cow , possibly due to higher CO2 emission. Capable of traveling several miles seeking blood meals and breeding sites.

Ecological Role

of large mammals; regulated by natural enemies including predatory mites (Macrocheles muscaedomesticae), (Muscidifurax spp., Spalangia spp.), and such as fire ants. Serves as prey for various . Can act as mechanical for including anthrax and potentially Anaplasma phagocytophilum.

Human Relevance

Major economic pest of livestock worldwide; described as the most costly pest of the US cattle industry. Economic injury occurs at thresholds of 2-4 flies per leg. Causes reduced weight gain (15-50% loss at high ), decreased milk production (15-30% documented), and anemia in severe cases. Bites are painful to humans, causing nuisance in recreational areas (beaches, parks) and occupational hazard for agricultural . Subject to intensive programs combining , , and chemical treatments. Research subject for modeling and olfactory sensory .

Similar Taxa

Musca domestica (House Fly)Similar size (~1/4 in. vs. 3/16 in.), gray coloration with thoracic stripes, and shared (Muscidae). Distinguished by house fly's sponging mouthparts (fleshy ) versus 's piercing proboscis; house flies do not bite.
Haematobia irritans (Horn Fly)Similar size, coloration, and blood-feeding habit. Distinguished by horn fly's continuous presence on animals versus 's habit of resting off-host; horn flies are slightly smaller and have different mouthpart structure.
Stomoxys nigra with overlapping distribution in some regions (e.g., Mauritius). S. nigra predominates in wetter, higher elevations while S. calcitrans is more abundant in drier, cooler conditions; S. nigra can reach higher densities.

More Details

Olfactory Ecology

Research demonstrates extremely sensitive olfactory detection capabilities. Stable flies can detect dimethyl trisulfide at thresholds comparable to octenol (used in mosquito traps), and are activated by volatile compounds from cattle rumen exhaled in breath. CO2 is a key attractant for both -seeking and oviposition .

Population Modeling

A 13-year study in Nebraska (2003-2015) capturing over 1.7 million flies developed predictive models showing that 70% of variability can be explained by temperature and precipitation alone, enabling more efficient timing of control interventions.

Insecticide Resistance

Subject to developing resistance to and ; management recommendations include rotating chemical classes and using threshold-based treatment timing to delay resistance development.

Phoretic Associations

Documented association with phoretic mites (Macrocheles muscaedomesticae) that attach to flies for ; first reported from Colombia in 2024.