horse fly

True flies in the family Tabanidae of the insect order Diptera are horse flies and deer flies. When flying, the adults are frequently big and nimble. Horseflies only bite females to acquire blood; they do not bite males. They are dormant at night and like to fly in bright light, avoiding shadowy and dark places. With the exception of a few islands and the polar areas (Hawaii, Greenland, Iceland), they can be found all over the world. It’s common to refer to horseflies and botflies (Oestridae) as gadflies.

The males of horseflies have weak mouthparts, and only the females bite animals to get enough blood protein to make eggs. Adult horseflies eat on nectar and plant exudates. Females have a robust, stabbing organ in their mouth that has two pairs of sharp teeth.
cutting blades and a component that resembles a sponge that is used to absorb blood dripping from cuts. The semiaquatic environments are home to the predaceous larvae.
Because of their feeding behavior, female horse flies have the ability to spread blood-borne illnesses from one animal to another. They have been reported to spread tularemia, anthrax in sheep and cattle, the filarial worm Loa loa, several trypanosomes, and the equine infectious anemia virus in disease-ridden areas. If appropriate shelters are not provided, they can slow down the growth rates of cattle and decrease the amount of milk produced by cows.
Since Aeschylus in Ancient Greece described horse-flies as driving individuals to “madness” by their relentless pursuit, they have been mentioned in literature.

Common names

There are numerous colloquial names for the Tabanidae family. The subfamily Chrysopsinae is commonly referred to as “deer flies,” maybe due to its profusion on moors where deer can be found, and the fact that other parts of the world are home to buffalo, moose, and elephant flies. The term “horse fly” mostly describes Tabaninae, which are usually larger, stouter, and do not have banded wings like deer flies do. Green-headed flies, tabanids, gadflies, and green flies are some more frequent names for them.

From Pliny the Younger’s first account, the word “Tabanus” has persisted as a generic name. Generally speaking, rural people referred to all of the biting insects that bothered their cattle as “gad-flies” because the word “gad” refers to a spike. Other colloquial terms are They have Old Norse origins and might have been Viking in origin. Other names, including “dun-flies” for their somber coloring and “stouts” for their broad bodies, describe the insects. March flies, a term used in other Anglophonic countries to denote to the non-bloodsucking Bibionidae, is another name for them in Australia and the UK.



Large flies with conspicuous compound eyes, short antennae made of three segments, and broad bodies are called adult tabanids. The eyes are widely spaced in females but nearly touching in males; in life, they are frequently patterned and colorful, but in preserved specimens, they seem boring. The antennae’s terminal segment is annulated, pointed, and gives the impression that it is composed of multiple tapering rings. The antennae do not have any arista or hairs emerging from them. There are small hairs covering the head and thorax, but the body is hairless. The transparent, consistently colored grey or brown, or patterned in certain species, membranous forewings feature a basal lobe, also called a calypter, that covers the modified knob-like hindwings, also known as halteres. The advice of the legs feature two claws that allow them to grasp surfaces, as well as two lobes on the sides called pulvilli and a center lobe called an empodium. Details of the head features (antennae, frons, and maxillae), the wing venation, and the body patterning are used to identify species; minute differences in surface structure result in minute changes to the overlaying hairs, which change the body’s appearance.

Distribution and habitat

With the exception of the polar areas, tabanids can be found all over the planet. However, some islands, such Greenland, Iceland, and Hawaii, do not have them.While Haematopota is not found in Australia or South America, the genera Tabanus, Chrysops, and Haematopota are all found in temperate, subtropical, and tropical regions. They inhabit a variety of habitats, from deserts to alpine meadows, although they are most common in warm climates with damp spots that are ideal for reproducing. They can be found at least 3,300 meters (10,800 feet) above sea level.

Evolution and taxonomy

The family’s earliest known fossils date back to the Early Cretaceous, with the Eotabanoid fossil found in the Purbeck Group of England’s Berriasian (145–140 million years ago) rocks. Even though a long proboscis is linked to the bloodsucking behavior, a fossil insect with elongated mouthparts may not have been a bloodsucker; it may have instead eaten on nectar. It’s possible that the angiosperm plants that the ancestral tabanids consumed coevolved with them. The early tabanomorph diet was most likely predatory due to their need for high-protein food for egg development; this may have led to the evolution of the bloodsucking habit. Since no mammals have been discovered in the Santana Formation of Brazil, it is most likely that the fossil tabanids there consumed reptiles. icy, bloodsucking Though warm-blooded dinosaurs are thought to have existed before warm bloodsucking, they could have served as early hosts for horse-flies.


The Diptera order of insects includes the real flies, or Tabanidae. The Tabanidae family is categorized in the superfamily Tabanoidea together with the families Athericidae, Pelecorhynchidae, and Oreoleptidae. This superfamily and the Rhagionoidea together comprise the infraorder Tabanomorpha. A venom tube in the larvae’s jaw appears to be a common feature among tabanoid groups. Approximately 1,300 of the 4,455 Tabanidae species that have been described are in the genus Tabanus.

The identification of tabanids is mostly dependent on the physical characteristics of the adult head, wing venation, and occasionally the final abdominal segment. The genitalia are quite basic and don’t offer any distinct species distinction, similar to that of many other insect taxa. Three subfamilies were previously thought to make up the family according to most taxonomic treatments: Tabaninae , Chrysopsinae and Pangoniinae .

Diet and biting behavior

Adult tabanids consume nectar and plant exudates; some are significant pollinators of specific specialized flowers. Several Asian and South African species of the Pangoniinae family have remarkably long probosces that are designed to extract nectar from flowers that have long, narrow corolla tubes, like some Pelargonium and Lapeirousia.

Males and females eat on nectar, but most species’ females are anautogenous, meaning they need a blood meal in order to successfully reproduce. The females bite humans and other animals to get blood, while the males do not do this. The female must find a new host once her blood meal has been entirely digested, which takes around six days. The movement, warmth, and prospective victim appear to draw the flies’ attention. Its surface roughness, as well as by the carbon dioxide it exhales. Large mammals like cattle, horses, camels, and deer are the primary targets of the flies, however, some are species-specific. They have also been seen consuming recently deceased animals, birds, lizards, turtles, and smaller mammals. In contrast to many other biting insects, like mosquitoes, whose saliva and biting mechanism enable a bite to occur without the host noticing it at the time, tabanid bites cause acute discomfort to the victim, which makes them frequently ignored. They may also need to bite several hosts in order to get enough blood. Because of their behavior, they could transfer pathogenic microbes from one host to another. Typically, large animals and livestock are unable to remove the fly, therefore the flies have no selection advantage to evolve a less painful bite right away.


Females have the typical dipteran mouthparts, which are made up of a bundle of six chitinous stylets that form the proboscis together with a fold in the fleshy labium. These have two maxillary palps on either side. The insect retracts its labium, thrusts its head downward, grips the surface with its clawed feet, and uses its stylets to sever flesh when it falls on an animal. Muscles can be used to move some of these sawing edges from side to side, enlarging the wound. To stop clotting, saliva containing an anticoagulant is injected into the wound. Another region of the mouth that acts as a sponge absorbs the blood that seeps from the wound. Bite discomfort can last for up to a day; Fly saliva can cause allergic reactions that include hives and breathing difficulties. Bites from tabanids can decrease a cow’s milk production and make living outside unpleasant for people. They are especially bothersome near swimming pools because they are drawn to polarized reflections from the water. Tabanids are nocturnal creatures that enjoy the sun, therefore they typically stay out of shady areas like barns.

Different species have different attack patterns: huge Tabanus species buzz loudly, fly low, and bite ankles, legs, or backs of knees; Chrysops flies somewhat higher, bites the back of the neck, and has a high buzzing tone. Clegs fly silently and prefer to bite humans on the wrist or bare leg. Zebras’ striped hides could have developed to lessen the allure of them to tsetse and horse flies. The zebra’s legs have especially fine striping, and this is the shadowed area of the body that is most likely to be bitten in other, unstriped equids. The closer the stripes are together, the less flies are visually drawn to the animal.

The same lead author’s more recent research demonstrates that tabanids found the stripes just as appealing, however they were only able to touch them rather than make a controlled landing to bite. This implies that obstructing optic flow was one of the stripes’ functions. This does not mean that stripes cannot be used for other functions, such camouflage or signaling. However, there might be another disruptive factor at work as well: a research evaluating the behavior of horseflies when they approach horses wearing either When striped or checkered carpets were compared to plain rugs, it was discovered that both patterns were just as successful in keeping insects away.



Especially on emergent water plants, eggs are placed in clusters of up to 1000 on stones or vegetation near bodies of water. The eggs are initially white but eventually turn black. After roughly six days, they hatch, and the emerging larvae use a unique hatching spike to crack open the egg case. The larvae drop to the damp ground below or into the water. Whereas Tabanus species favor drier environments, Chrysops species thrive in exceptionally moist environments. The larvae are tapered at both ends, legless grubs. They have little heads with eleven or thirteen segments, and they shed their skin six to thirteen times in a year or longer. While tropical species spawn multiple times during the winter, temperate species’ larvae have a quiescent phase known as the diapause one year. They are white in most species, but some are green or brown in color, and each segment frequently has dark bands. When submerged in water, the larvae can breathe thanks to a respiratory siphon at the hind end.

Almost all species’ larvae are carnivorous; in captivity, they frequently exhibit cannibalism and eat worms, insect larvae, and arthropods. Nematodes, flies from the Tachinidae and Bombyliidae families, and Hymenoptera from the Pteromalidae family can parasitize the larvae. When fully grown, the larvae go to drier soil close to the ground’s surface to pupate. W.A. Lamborn found a “remarkable” adaption to arid environments in Malawi (formerly Nyasaland) in the 1920s. It was found that the larvae tunneled in a While the mud was still plastic and wet, the larva moved in a spiral motion, creating a partitioned cylinder in the center of which it settled to pupate after sealing the entrance. This adaptation shields the pupae from mudcracks when the mud dries up because a spreading crack would reorient itself when it struck the cylinder wall.

The glossy, brown pupae have a tapering tip at one end and a spherical head. Each abdominal segment is rimmed with tiny spines, and wing and limb buds are visible.

Predators and parasites

Tiny parasitic wasps frequently attack eggs, and birds eat the larvae in addition to fungus, nematodes, and tachinid flies paratizing them. Generalized predators like birds consume adults, and certain specialized predators like the horse guard wasp (a bembicinid wasp) attack horse flies more frequently in order to capture them for their nests.

As disease vectors

Certain blood-borne bacterial, viral, protozoan, and worm illnesses of mammals, including the horse infectious anemia virus and several Trypanosoma species that infect people and animals, are known to be transmitted by tabanids. Humans can contract the parasitic filarial worm Loa loa from species of the genus Chrysops, whereas cattle, sheep, and humans can contract tularemia from tabanids.

In several animals, blood loss is a regular issue during periods of high fly abundance. It has been reported that tabanid flies can cause an animal to lose up to 300 ml (11 imp fl oz; 10 US fl oz) of blood in a single day, which can weaken or even kill the animal. Anecdotal evidence of bites resulting in anaphylactic deaths in It is incredibly uncommon that people have been created.


Tabanid flies are hard to control. The most common method of catching them is with malaise traps, which can be altered by adding attractants and baits like octenol or carbon dioxide. They can also be drawn to a black, shiny ball that is hung underneath them and moves with the breeze. This ball is an essential component of a modified “Manitoba trap,” which is most frequently employed to catch and collect Tabanidae samples. Pour-on pyrethroids can be used to treat cattle to deter flies, and attaching collars or eartags containing insecticide has been partially successful in eliminating the insects.


Humans may experience pain from tabanid bites. Weals, or elevated patches of skin, typically develop around the site; further symptoms could include asthma, dizziness, weakness, urticaria, and angioedema, which is a transient, itchy, pink or red swelling around the lips or eyes. Allergies affect a small percentage of persons. It is advised by the National Health Service of the United Kingdom to cleanse the bite site and apply a cold compress. It is best to keep your wound from being scratched, and you can use an antihistamine preparation. Most of the time, the symptoms go away in a few hours, but you should see a doctor if the wound becomes infected.


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