Stomoxys calcitrans

Geographic Range

Stomoxys calcitrans is a cosmopolitan insect, meaning that it can be found worldwide as long as suitable food and weather conditions can be met.


The habitat of the stable fly, as suggested by its common name, is almost anywhere that horses, cattle, and other agricultural animals can be found (especially inside barns and stables). (Bishop, 1913; Janovy and Roberts, 2000)

Physical Description

The stable fly closely resembles the common housefly (Musca domestica). Unlike the common housefly, Stomoxys calcitrans have a broader abdomen. Adult stable flies average 8 mm in length, have a gray body, and can be identified by four characteristic longitudinal stripes across the thorax as well as several dark spots on top of the abdomen. On the vertex and frons there are three ocelli and two large compound eyes. Sexual dimorphism occurs in this species, and there is more distance between the compound eyes in females. The proboscis of the stable fly is black, long, and thin, protruding from the front of the head. Its other mouthparts are modified, with the labellum having rows of teeth in order to pierce the skin of its host. The palps are one third of the length of the proboscis.

Larvae range in size from 5 to 12 mm long. Mature larvae are yellowish white maggots, and are a cylindrical shape that tapers anteriorly.. The pupae have a reddish-to-dark brown exterior and are 4 to 7 mm long. The posterior spiracles on the puparia are black with three S-shaped yellow slits, and are lightly sclerotized. (Bishop, 1913)

  • Sexual Dimorphism
  • female larger
  • Average length
    8 mm
    0.31 in


Stomoxys calcitrans eggs take one to four days to develop. The length of this period is affected by temperature, humidity, and how long the egg was retained by the female. The larval stage lasts from 11 to 30 (and sometimes more) days, based upon habitat suitability and availability of food. After the third instar (growth stage) the maggot will pupate for 6 to 20 days. As with larval maturation, length of pupation is based upon food abundance and quality during larval growth. (Bishop, 1913)


The stable fly breeds in a number of habitats commonly found in agricultural areas such as decaying straw, oats, rice, barley, wheat, silage, horse manure, lot manure (manure from pig farms), and cow manure. (Bishop, 1913; Hunter and Curry, 2001)

The female must be engorged for reproduction. The female never oviposits before the third feeding and, on average; four engorgements are necessary before eggs can be laid. The female has a greatly extended pseudovipositor with which she deposits eggs into decaying straw where there is moisture. Eggs are laid singly, or in bunches of 25 or 30. This activity usually lasts for about half an hour. (Bishop, 1913)

Eggs are laid in a habitat that will provide food suitable for larval growth and development. After eggs are laid, there is no further parental investment.

  • Parental Investment
  • pre-fertilization
    • provisioning
    • protecting
      • female


Soon after mating males die. Females die soon after laying their eggs.


Stomoxys calcitrans locates its host by sight. On cattle it will first land and rest on the back of the animal. As soon as it is disturbed, it flies to the outside of the forelegs; where it will bite the cow near the knees and begin feeding. On horses S. calcitrans prefers feeding on the sides of the neck, lower legs, and underbelly. After feeding, S. calcitrans rests nearby, usually on warm, sunny sites such as fences, walls and vegetation near the hosts. When disturbed it will fly and then return to the original spot of feeding. (Bishop, 1913)

Communication and Perception

These flies have good eyesight and communicate visually.

  • Communication Channels
  • visual

Food Habits

Stomoxys calcitrans is a daytime feeder. The adults of both sexes feed on blood. There is low host specificity; although they feed mainly on the blood of cattle and horses. Adults locate a host by sight, and feeding is usually completed in two to five minutes. After feeding the stable fly is sluggish, and remains motionless near the host. The stable fly will generally feed from many hosts before it is replete. Studies show that there is a rise in feeding during warm wether, whereas there is a decrease in feeding rates during rain. After hatching, the larvae begin feeding on local microbial flora and fauna. (Bishop, 1913; Janovy and Roberts, 2000; Bishop, 1913; Janovy and Roberts, 2000)

  • Animal Foods
  • mammals
  • blood


There is little known predation of this species.

Economic Importance for Humans: Positive

There is no obvious human benefit provided by these flies.

Economic Importance for Humans: Negative

Stomoxys calcitrans economically affects humans in two ways: livestock reduction and disease. The accumulation of stable fly bites leads to a certain degree of anemia, weight loss in cattle, reduced milk production in dairy cattle. In this way, S. calcitrans costs the US millions of dollars. It also affects the cattle industry by destroying the hides of cattle due to the holes created by the piercing of the skin for feeding.

Studies have shown that as few as 20 flies per animal can reduce the rate of milk production. The effect on the hosts increases proportionally with an increase in the number of bites. This trend eventually reaches a plateau, due to the fact that the stable fly is only a daytime feeder.

For ox, horses, and sheep, S. calcitrans is a vector of Trypansoma cazalboui. This parasite causes the disease known as souma. For ox, it is a vector of T. pecaudia. For domestic animals and humans it is a vector of anthrax. This disease can cause a number of different symptoms, inculding lesions in the lungs and brain. It is also a vector for T. evansi (the agent of Surra), T. brucei, ERF, brucellosis, swine erysipelcs, equine swamp fever, African horse sickness, and fowl pox. (Bishop, 1913; Catangui, et al., 1993; Cook, et al., 1999; Janovy and Roberts, 2000)

Conservation Status

This species has large populations world-wide, and is in no danger of extinction.

Other Comments

This species was introduced to North America in the 1700's. (Bishop, 1913)


Sara Diamond (editor), Animal Diversity Web.

Jennifer Newberry (author), University of Michigan-Ann Arbor, Teresa Friedrich (editor), University of Michigan-Ann Arbor.



Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

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living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

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living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

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living in the southern part of the New World. In other words, Central and South America.

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living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

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living in landscapes dominated by human agriculture.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


an animal that mainly eats meat

causes disease in humans

an animal which directly causes disease in humans. For example, diseases caused by infection of filarial nematodes (elephantiasis and river blindness).

causes or carries domestic animal disease

either directly causes, or indirectly transmits, a disease to a domestic animal


having a worldwide distribution. Found on all continents (except maybe Antarctica) and in all biogeographic provinces; or in all the major oceans (Atlantic, Indian, and Pacific.

  1. active during the day, 2. lasting for one day.

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature


union of egg and spermatozoan


having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

internal fertilization

fertilization takes place within the female's body


referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.


A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.


having the capacity to move from one place to another.


found in the oriental region of the world. In other words, India and southeast Asia.

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reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.


an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death


an animal that mainly eats blood


reproduction that includes combining the genetic contribution of two individuals, a male and a female


lives alone


living in residential areas on the outskirts of large cities or towns.


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


Living on the ground.


the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.


A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.


uses sight to communicate


Bishop, F. 1913. The Stable Fly (Stomoxys caclitrans L.) An Important Live Stock Pest. Journal of Economic Entomology, 6: 112-126.

Catangui, M., J. Cambell, G. Tomas, D. Boxler. 1997. Calculating Economic Injury Levels for Stable Flies (Diptera: Muscida) on Feeding Heifers. Journal of Economic Entomology, 90(1): 6-10.

Catangui, M., J. Cambell, G. Tomas, J. Boxler. 1993. Average Daily Gains of Brahman-cross-bred and English X Exotic Feeder Heifers Exposed to Low, Medium, and High Levels of Stable Flie.. Journal of Economic Entomology, 86: 1114-1150.

Cook, D., I. Dadour, N. Keals. 1999. Stable Fly, House Fly (Diptera: Muscidae), and other Nuisance Fly Development in Poultry Litter Association with Horticultural Crop Production. Journal of Economic Entomology, 92(6): 1352-7.

Hunter, G., P. Curry. 2001. "AgResource" (On-line). Accessed February 22, 2005 at

Janovy, J., L. Roberts. 2000. Foundations of Parasitology, 6th Edition. USA: The McGraw-Hill Companies, Inc..