Stomoxys calcitrans — stable fly

The stable fly Stomoxys calcitrans occurs around the world. The life cycle involves egg laying in faeces or decaying and damp organic material, for example straw bedding.


The stable fly Stomoxys calcitrans occurs around the world.  The life cycle involves egg laying in faeces or decaying and damp organic material, for example straw bedding.  The larva that develops within each egg hatches and pupates and the adult fly is released from the pupa.   Male and female stable flies will blood feed on most domestic animal species and the bites can be very troublesome and can interfere with livestock production.  Stable flies are the intermediate host for the gastric nematodes Habronema and Draschia  of horses, which are thought to occur only rarely in Canada.  Also, stable flies tend to feed rapidly and to bite several animals in quick succession.  As a result, in other parts of the world stable flies can act as mechanical vectors (transport not intermediate hosts) for a variety of pathogens, especially several species of the protozoan Trypanosoma infecting people and/or domestic animals and/or people.


Phylum: Arthropoda
Subphylum: Uniramia
Class: Hexapoda
Subclass: Pterygota
Order: Diptera
Family: Muscidae

The closest relatives to S. calcitrans are probably flies within the genera Musca (including the house fly, Musca domestica) and Haematobia (including the horn fly, Haematobia irritans).

Note: Our understanding of the taxonomy of helminth, arthropod, and particularly protozoan parasites is constantly evolving. The taxonomy described in wcvmlearnaboutparasites is based on that in the seventh edition of Foundations of Parasitology by Larry S Roberts and John Janovy Jr., McGraw Hill Higher Education, Boston, 2005.


Adult Stomoxys are approximately the same size as a house fly (usually less than 8 mm in length), with an obvious, forward-pointing proboscis and long antennae. The thorax is marked with four longitudinal dark stripes, and there are three dark spots on the middle two of the four abdominal segments.

Host range and geographic distribution

Adult male and female stable flies blood feed on a wide variety of mammals, including people, as well as birds and sometimes reptiles. Stomoxys calcitrans occurs around the world.

Life cycle - direct

Adult female S. calcitrans need several blood meals prior to laying eggs, which they do in fresh horse manure or in moist rotting vegetation, particularly hay or straw that has been contaminated with urine. The larva hatches from the egg, moults through three instars, and then pupates. In ideal conditions, the entire life cycle can be completed in approximately two weeks. The adult flies can survive for approximately one month, and longer in cooler temperatures.

Life Cycle: Stomoxys calcitrans


The basic feeding (biting) pattern for S. calcitrans is diurnal, with peaks of activity around sunrise and sunset. The flies prefer bright light and rarely enter buildings.

Pathology and clinical signs

Bites by S. calcitrans can be very painful, and tend to be more common on the lower parts of the body, including the legs and the ventral abdomen and thorax. Biting by stable flies is a major source of annoyance, and horses, cattle, sheep and other livestock can be affected, together with wildlife and people. Biting by these flies can seriously interfere with milk and meat production in cattle and other livestock.

Stomoxys calcitrans can act as transport (not intermediate) hosts for a range of trypanosome species in tropical areas, including Trypanosoma brucei rhodesiense and T. b. gambiense of people and T. b. brucei and T. vivax of animals.


Other than perhaps by location on the animal, it is impossible to differentiate stable fly bites from those of other biting insects.

Treatment and control


Myrna, won't transfer




Public health significance

Stable flies can be serious pests of people as a result of their biting activity, and can also act as transport (not intermediate) hosts for the trypanosomes causing sleeping sickness in people in Africa.
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