Derivation of scientific name: The name Stomoxys calcitrans comes from the Ancient Greek words stóma (mouth) and oxús (sharp, keen). The name translates to ‘sharp mouth’ and ‘kicking’.
Common names: Stable fly, biting house fly (Eng.)
The stable fly, Stomoxys calcitrans, is nature’s miniature vampire with an interesting twist: both men and females consume blood, making them an ‘equal opportunity’ pest. By torturing livestock such as cattle with their painful, stiletto-like mouthparts, these resilient insects, which are known as biting house flies or stable flies cause billions of dollars’ worth of agricultural losses every year.
Their amazing capacity to sense carbon dioxide, body heat and even the special combination of chemicals in animal breath allows them to locate and track their hosts from a great distance. These flies’ tendency for biting their victims’ legs, especially in the hours preceding a storm when the lowering barometric pressure appears to set off a feeding frenzy, adds to their mystique.
Stomoxys calcitrans (Linnaeus, 1758) is among the most widely distributed blood feeding Diptera species affecting man and animals (Showler & Osbrink 2015). They are hematophagous flies, with adults needing multiple bloodmeals per day for successful mating and development of eggs (Mullen & Durden 2009).
Description/how to recognise a stable fly
Several distinguishing characteristics differentiate a stable fly from the common house fly, despite its similar size (about 5–7 mm long) and grey colour (Bishopp 1913). The stable fly’s most distinctive feature is a prominent black, bayonet-like proboscis that protrudes forward from behind its head.
It has dark markings on its thorax and a checkered black-and-grey pattern on its abdomen. When at rest, its wings, held at a 45° angle from the body, make a characteristic V-shape. They have eggs that are 1 mm in length, white and sausage shaped. The larvae, a yellowish-white maggot, ranges between 1 mm to 12 mm in length, cylindrical in shape, while the pupae is 4–7 mm in size and is reddish to dark brown in colour (Tawich et al. 2021).
In terms of behaviour, they are more frequently seen near and around livestock facilities (Baldacchino et al. 2013). Both males and females are aggressive blood eaters that attack human and animal legs (Bishopp 1913).
Getting around
Stable flies move around on their hosts. When temperatures are less than 30°C stable flies will be active on the sunny side of the host, while when temperatures are greater than 30°C, they will be active on the shaded parts of the host (Showler & Osbrink 2015).
Stable flies spread by both active flight and passive transport. With the help of their strong wings, these flies actively fly for long distances on their own in search of hosts and potential mating grounds (Showler & Osbrink, 2015). Their distribution is greatly aided by wind currents, which can occasionally carry them longer distances.
When stable fly host animals migrate or are moved between areas, these flies track their movements, especially those of livestock herds (Allan 2001). Stable flies have been known to travel up to several hundred kilometres using a combination of active flight and wind-assisted dispersal, although they usually remain within a few kilometres of their nesting locations when conditions are appropriate. Seasonal fluctuations significantly influence their migration patterns; populations often migrate annually in pursuit of improved breeding and feeding conditions.
Communication
The complex range of communication techniques used by stable flies mostly centres around chemical and visual cues. Pheromones, which are chemical messengers that are essential to mate attraction and aggregation behaviours, are at the core of their communication system.
They have particular pheromones that they use to create groups and to find possible partners and appropriate nesting locations. During courting, the males use unique flying patterns and wing movements to draw attention of the females, indicating the importance of visual communication (Eichorn et al. 2017).
Their communication skills also extend to finding hosts, where they exhibit exceptional proficiency in identifying possible victims by utilising a complex array of signals, such as body heat, carbon dioxide emissions and chemical components found in animal sweat and breath.
In addition to this, physical communication is essential during mating where movement such as vibrations covey important information for the individuals. Stable flies can efficiently reproduce, locate food sources and sustain their numbers because to this complex communication network (Foil & Hogsette 1994).
Distribution
Stable flies are a cosmopolitan species, which means they have been found on all inhabited continents (Duvallet & Hogsette 2023). In temperate, subtropical and tropical regions, these flies are particularly prevalent in areas with livestock operations and agricultural activities. Stable flies thrive in coastal areas, agricultural landscapes and around animal facilities (Showler & Osbrink 2015).
Their distribution is closely tied to human activities, particularly animal husbandry and crop production, as these provide ideal breeding conditions in the form of decomposing vegetation and animal waste (Rochon et al. 2021).
While they originated in the Old World, likely in the Afrotropical region, stable flies have successfully established themselves globally through human commerce and livestock movement. Their ability to adapt to various climates and habitats has enabled them to become cosmopolitan pests, though their abundance may fluctuate seasonally within different regions.
Habitat
The stable fly is found in stables and near agricultural animals in moist, decaying organic matter, such as animal manure, hay and the residue of crops. These flies thrives in a variety of habitats that provide the necessary conditions for both adult survival and larval development.
The adult flies prefer warm, humid environments (Cook 2020). The larvae specifically require moist, decomposing organic matter for development, often found in areas where vegetation and animal manure mix together.
These breeding sites are typically characterised by ambient temperatures between 22 and 28°C and moisture content of 40–60%. In urban and suburban settings, they can establish themselves wherever suitable organic waste accumulates, including garden compost piles (Thibodeaux et al. 2021).
Food
These flies tend to feed on the blood of big animals, such as livestock like cattle and horses, but they can also feed on goats, sheep, swine, donkeys, cats, dogs and humans (Thibodeaux et al. 2021).
The flies flock together on the legs and proceed to other parts such as the stomach and lower sides on large animals and around the ears, head and legs on smaller animals (Sarwar 2020).
SEX AND LIFE CYCLES
Sex: Stable flies reproduce in damp, rotting material that is rich in organic matter. A female stable fly may lay up to 800 eggs in its life time in small clutches of about 25-30 at a time.
Depending on the amount of moisture and food available, the lifecycle of a stable fly may take 11 to 30 days. The male stable fly will die after mating while the female dies soon after laying its eggs (Olafson et al. 2021).
Family life: Unlike most truly social insects, stable flies lack structured social communities and hierarchical behaviours. Although they occur in large numbers around feeding and breeding sites, these gatherings result from environmental conditions and resource availability rather than social organisation.
Their only intraspecific contacts are during mating, in which males engage in a straightforward competition for females devoid of formal social organisation. While larvae develop near each other in breeding materials, this proximity stems from females selecting the same favourable egg-laying locations rather than social behaviour or cooperation.
Stable flies, in contrast to ants or bees, are motivated only by the basic demands for blood meals, mates and adequate breeding places.
THE BIG PICTURE
Friends and foes
Stable flies involved in diverse ecological interactions throughout the food web (Skevington & Dang 2002). These flies serve as prey for birds, spiders, wasps and reptiles, while their larvae fall victim to beetles, mites and soil predators (Skevington & Dang 2002). These flies compete with other blood-feeding insects for host availability and for breeding resources.
As vectors for diseases, they have the ability to mechanically transmit various pathogens between animals, affecting livestock, wildlife and humans (Baldacchino et al. 2013). Stable fly populations are naturally controlled by parasitic wasps, entomopathogenic fungi, predatory arthropods and pathogenic microorganisms.
They also maintain indirect symbiotic relationships with decomposer microbes that create favourable conditions for larval development in organic matter (Galante & Marcos 2008). Despite their ecological importance, stable flies are primarily regarded as agricultural and urban pests due to their blood-feeding habits and disease transmission capabilities.
Smart strategies
Stable flies have evolved several clever survival strategies that showcase their adaptability. They also demonstrate impressive host-targeting intelligence by preferentially attacking the lower legs of animals, a location that’s hard for the host to defend and offers easy access to blood vessels (Dougherty et al. 1993).
Their breeding strategy is equally sophisticated as they carefully select fermented organic matter like aging hay or manure for egg-laying, ensuring their larvae will have the perfect warm, moist environment rich in decomposing vegetation for development.
They’ve also evolved to be opportunistic/parasitic feeders, capable of drawing blood from multiple host species, which significantly increases their survival chances when preferred hosts are scarce. These flies hare capable of traveling several kilometres to find new hosts or breeding sites when local conditions become unfavourable (Showler & Osbrink 2015).
Poorer world without me
From a purely economic perspective, their absence would seemingly benefit the livestock industry, which loses billions annually to these pests. However, from an ecological standpoint, stable flies do play several important roles. They serve as decomposers in their larval stage, helping break down organic matter like manure and vegetation. They’re also part of the food web, providing sustenance for various predatory insects, birds, and other animals.
People and I
Stable flies don’t show up much in old stories and myths, unlike mosquitoes and other biting insects. This is probably because people mostly saw them bothering farm animals rather than causing problems for humans directly.
However, in some agricultural communities, particularly in parts of Africa, there are many beliefs that connect increased stable fly activity with imminent weather changes, specifically approaching storms, which is a belief that actually has some scientific merit due to the flies’ sensitivity to barometric pressure changes.
In some farming traditions, they were seen as indicators of poor livestock health and declining farm productivity. Their biting behaviour can reduce milk production in dairy cattle, decrease weight gain in beef cattle, and impact the overall health and productivity of various livestock. The global economic impact from stable flies is estimated to be in the billions of dollars annually.
Conservation status and what the future holds
Stable flies are classified as species of Least Concern in terms of conservation status, which is not surprising given their global distribution and remarkable adaptability. These resilient insects are found on every inhabited continent and have demonstrated an impressive ability to thrive in diverse environments, particularly where humans and livestock are present (Duvallet & Hogsette 2023).
Looking toward the future, several factors seem likely to influence their populations and distribution. Climate change could significantly impact their range – warming temperatures might extend their viable habitat into previously inhospitable regions, while also potentially making some current habitats less suitable.
Increasing global livestock production, particularly in developing nations, could provide more abundant food sources and breeding sites for these flies. However, advancing pest management technologies and changing agricultural practices, such as improved waste management systems and biological control methods, might help reduce their populations in managed settings.
Official common name: Stable fly
Scientific name and classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Diptera
Family: Muscidae
Genus: Stomoxys
Species: S. calcitrans (Linnaeus, 1758)
References and further reading
- Allan, S.A. 2001. Biting flies (class Insecta: order Diptera). Parasitic diseases of wild mammals, pp.18–45
- Baldacchino, F., Muenworn, V., Desquesnes, M., Desoli, F., Charoenviriyaphap, T. & Duvallet, G. 2013. Transmission of pathogens by Stomoxys flies (Diptera, Muscidae): a review. Parasite 20: 26.
- Bishopp, F.C. 1913. The stable fly (Stomoxys Calcitrans). Journal of Economic Entomology 6: 112.
- Cook, D. 2020. A historical review of management options used against the stable fly (Diptera: Muscidae). Insects 11(5): 313.
- Dougherty, C.T., Knapp, F.W., Burrus, P.B., Willis, D.C., Burg, J.G., Cornelius, P.L. & Bradley, N.W. 1993. Stable flies (Stomoxys calcitrans) and the behavior of grazing beef cattle. Applied Animal Behaviour Science 35(3): 215–233.
- Duvallet, G. & Hogsette, J.A. 2023. Global diversity, distribution, and genetic studies of stable flies (Stomoxys). Diversity 15(5): 600.
- Eichorn, C., Hrabar, M., Van Ryn, E.C., Brodie, B.S., Blake, A.J. & Gries, G. 2017. How flies are flirting on the fly. BMC biology 15: 1–10.
- Foil, L.D. & Hogsette, J.A. 1994. Biology and control of tabanids, stable flies and horn flies. Revue scientifique et technique-Office international des épizooties 13(4): 1125–1158.
- Galante, E. & Marcos-Garcia, M.A. 2008. Decomposer insects. Encyclopedia of Entomology, pp.1158–1169.
- Muenworn, V., Duvallet, G., Thainchum, K., Tuntakom, S., Tanasilchayakul, S., Prabaripai, A., Akratanakul, P., Sukonthabhirom, S. & Chareonviriyaphap, T. 2010. Geographic distribution of Stomoxyine flies (Diptera: Muscidae) and diurnal activity of Stomoxys calcitrans in Thailand. Journal of Medical Entomology 47(5): 791–797.
- Mullen, G.R. & Durden, L.A. (eds). 2009. Medical and veterinary entomology. Academic Press.
- Olafson, P.U., Aksoy, S., Attardo, G.M., Buckmeier, G., Chen, X., Coates, C.J., Davis, M., Dykema, J., Emrich, S.J., Friedrich, M. & Holmes, C.J. 2021. The genome of the stable fly, Stomoxys calcitrans, reveals potential mechanisms underlying reproduction, host interactions, and novel targets for pest control. Bmc Biology 19: 1–31.
- Patra, G., Behera, P., Das, S.K., Saikia, B., Ghosh, S., Biswas, P., Kumar, A., Alam, S.S., Kawlni, L., Lalnunpuia, C. & Lalchhandama, C. 2018. Stomoxys calcitrans and its importance in livestock. J. Adv. Agric. Res 6: 30–37.
- Rochon, K., Hogsette, J.A., Kaufman, P.E., Olafson, P.U., Swiger, S.L. & Taylor, D.B. 2021. Stable fly (Diptera: Muscidae) – biology, management, and research needs. Journal of Integrated Pest Management 12(1): 38.
- Sarwar, M. 2020. Typical flies: Natural history, lifestyle and diversity of Diptera. Life Cycle and Development of Diptera, pp.1–50.
- Showler, A.T. & Osbrink, W.L. 2015. Stable fly, Stomoxys calcitrans (L.), dispersal and governing factors. International Journal of Insect Science 7: IJIS-S21647.
- Skevington, J.H. & Dang, P.T. 2002. Exploring the diversity of flies (Diptera). Biodiversity 3(4): 3–27.
- Tawich, S.K., Bargul, J.L., Masiga, D. & Getahun, M.N. 2021. Supplementing blood diet with plant nectar enhances egg fertility in Stomoxys calcitrans. Frontiers in Physiology 12:
- Thibodeaux, R.J., Brady, J.A., Maryak, C.C.K., Swiger, S.L. & Jones, B.W. 2021. Screening stable flies and house flies as potential vectors of digital dermatitis in dairy cattle. Journal of Dairy Science 104(1): 977–980.
Authors: Veronica Phetla and Hlumela Nkwelo
E-mail: v.phetla@sanbi.org.za