Horse-flies or horseflies are true
flies
Flies are insects of the order Diptera, the name being derived from the Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced m ...
in the family Tabanidae in the
insect
Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three ...
order Diptera. They are often large and agile in flight, and only the female horseflies bite animals, including humans, to
obtain blood. They prefer to fly in sunlight, avoiding dark and shady areas, and are inactive at night. They are found all over the world except for some islands and the polar regions (Hawaii, Greenland, Iceland
). Both horse-flies and
botflies (Oestridae) are sometimes referred to as gadflies.
Adult horse-flies feed on nectar and plant
exudates; the males have weak
mouthparts and only the females bite animals to obtain enough
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...
from blood to produce
egg
An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the a ...
s. The mouthparts of females are formed into a stout stabbing organ with two pairs of sharp cutting blades, and a spongelike part used to lap up the blood that flows from the wound. The larvae are
predaceous
Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill the ...
and grow in semiaquatic habitats.
Female horse-flies can
transfer
Transfer may refer to:
Arts and media
* ''Transfer'' (2010 film), a German science-fiction movie directed by Damir Lukacevic and starring Zana Marjanović
* ''Transfer'' (1966 film), a short film
* ''Transfer'' (journal), in management studies
...
blood-borne disease
A blood-borne disease is a disease that can be spread through contamination by blood and other body fluids. Blood can contain pathogens of various types, chief among which are microorganisms, like bacteria and parasites, and non-living infectious ...
s from one animal to another through their feeding habit. In areas where diseases occur, they have been known to carry
equine infectious anaemia virus, some
trypanosomes
Trypanosomatida is a group of kinetoplastid excavates distinguished by having only a single flagellum. The name is derived from the Greek ''trypano'' (borer) and ''soma'' (body) because of the corkscrew-like motion of some trypanosomatid species. ...
, the
filarial worm ''
Loa loa
''Loa loa'' is a filarial (arthropod-borne) nematode (roundworm) that causes ''Loa loa'' filariasis. ''Loa loa'' actually means "worm worm", but is commonly known as the "eye worm", as it localizes to the conjunctiva of the eye. ''Loa loa'' is ...
'',
anthrax among cattle and sheep, and
tularemia
Tularemia, also known as rabbit fever, is an infectious disease caused by the bacterium ''Francisella tularensis''. Symptoms may include fever, skin ulcers, and enlarged lymph nodes. Occasionally, a form that results in pneumonia or a throat infe ...
. They can reduce growth rates in cattle and lower the milk output of cows if suitable shelters are not provided.
Horse-flies have appeared in literature since
Aeschylus
Aeschylus (, ; grc-gre, Αἰσχύλος ; c. 525/524 – c. 456/455 BC) was an ancient Greek tragedian, and is often described as the father of tragedy. Academic knowledge of the genre begins with his work, and understanding of earlier Greek ...
in
Ancient Greece
Ancient Greece ( el, Ἑλλάς, Hellás) was a northeastern Mediterranean Sea, Mediterranean civilization, existing from the Greek Dark Ages of the 12th–9th centuries BC to the end of Classical Antiquity, classical antiquity ( AD 600), th ...
mentioned them driving people to "madness" through their persistent pursuit.
Common names
![Micrographia Robert Hooke 24](https://upload.wikimedia.org/wikipedia/commons/e/ec/Micrographia_Robert_Hooke_24.png)
Apart from the common name "horse-flies", broad categories of biting, bloodsucking Tabanidae are known by a large number of common names. The word "Tabanus" was first recorded by
Pliny the Younger and has survived as the generic name. In general, country folk did not distinguish between the various biting insects that irritated their cattle and called them all "gad-flies", from the word "gad" meaning a spike. The most common name is "cleg
, "gleg" or "clag", which comes from
Old Norse
Old Norse, Old Nordic, or Old Scandinavian, is a stage of development of North Germanic dialects before their final divergence into separate Nordic languages. Old Norse was spoken by inhabitants of Scandinavia and their overseas settlemen ...
and may have originated from the
Vikings
Vikings ; non, víkingr is the modern name given to seafaring people originally from Scandinavia (present-day Denmark, Norway and Sweden),
who from the late 8th to the late 11th centuries raided, pirated, traded and ...
.
[ Other names such as "stouts" refer to the wide bodies of the insects and "dun-flies" to their sombre colouring. ''Chrysops'' species are known as "deer-flies", perhaps because of their abundance on moorland where ]deer
Deer or true deer are hoofed ruminant mammals forming the family Cervidae. The two main groups of deer are the Cervinae, including the muntjac, the elk (wapiti), the red deer, and the fallow deer; and the Capreolinae, including the re ...
roam,[ and "buffalo-flies", "moose-flies" and "elephant-flies" emanate from other parts of the world where these animals are found.][ In North America they are known as "horse flies" or "breeze-flies", and in Australia and the UK they are known as "March flies", a name used in other Anglophonic countries to refer to the non-bloodsucking ]Bibionidae
Bibionidae (March flies) is a family of flies ( Diptera) containing approximately 650–700 species worldwide. Adults are nectar feeders and emerge in numbers in spring. Because of the likelihood of adults flies being found ''in copula'', they ...
.
Description
Adult tabanids are large flies with prominent compound eyes
A compound eye is a visual organ found in arthropods such as insects and crustaceans. It may consist of thousands of ommatidia, which are tiny independent photoreception units that consist of a cornea, lens, and photoreceptor cells which distin ...
, short antennae composed of three segments, and wide bodies. In females, the eyes are widely separated but in males, they are almost touching; they are often patterned and brightly coloured in life but appear dull in preserved specimens. The terminal segment of the antennae is pointed and is annulated, appearing to be made up of several tapering rings. There are no hairs or arista arising from the antennae. Both head and thorax are clad in short hairs, but no bristles are on the body. The membranous forewings are clear, uniformly shaded grey or brown, or patterned in some species; they have a basal lobe (or calypter) that covers the modified knob-like hindwings or halteres
''Halteres'' (; singular ''halter'' or ''haltere'') (from grc, ἁλτῆρες, weights held in the hands to give an impetus in leaping) are a pair of small club-shaped organs on the body of two orders of flying insects that provide infor ...
. The tips of the legs have two lobes on the sides (pulvilli) and a central lobe or empodium in addition to two claws that enable them to grip surfaces. Species recognition is based on details of head structures (antennae, frons
Insect morphology is the study and description of the physical form of insects. The terminology used to describe insects is similar to that used for other arthropods due to their shared evolutionary history. Three physical features separate insec ...
, and maxillae
The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The t ...
), the wing venation and the body patterning; minute variations of surface structure cause subtle alterations of the overlying hairs which alters the appearance of the body.[
Tabanid species range from medium-sized to very large, robust insects. Most have a body length between , with the largest having a wingspan of .] Deer flies in the genus ''Chrysops
Deer flies (also known in some parts of the mid-Atlantic United States as sheep flies) are bloodsucking insects considered pests to humans and cattle. They are large flies with large brightly-coloured compound eyes, and large clear wings with da ...
'' are up to long, have yellow to black bodies and striped abdomens, and membranous wings with dark patches. Horse-flies (genus ''Tabanus
''Tabanus'' is a genus of biting horseflies of the family Tabanidae. Females have scissor-like mouthparts that aim to cut the skin. The horsefly can then lap up the blood. Horseflies of this genus are known to be potential vectors of anthrax, ...
'') are larger, up to in length and are mostly dark brown or black, with dark eyes, often with a metallic sheen. Yellow flies (genus '' Diachlorus'') are similar in shape to deer flies, but have yellowish bodies and the eyes are purplish-black with a green sheen. Some species in the subfamily Pangoniinae have an exceptionally long proboscis
A proboscis () is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular mouthparts used for feeding and sucking. In vertebrates, a proboscis is an elong ...
(tubular mouthpart).
The larvae are long and cylindrical or spindle-shaped with small heads and 12 body segments. They have rings of tubercle
In anatomy, a tubercle (literally 'small tuber', Latin for 'lump') is any round nodule, small eminence, or warty outgrowth found on external or internal organs of a plant or an animal.
In plants
A tubercle is generally a wart-like projection ...
s (warty outgrowths) known as pseudopods around the segments, and also bands of short seta
In biology, setae (singular seta ; from the Latin word for " bristle") are any of a number of different bristle- or hair-like structures on living organisms.
Animal setae
Protostomes
Annelid setae are stiff bristles present on the body. ...
e (bristles). The posterior tip of each larva
A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle.
...
has a breathing siphon and a bulbous area known as Graber's organ. The outlines of the adult insect's head and wings are visible through the pupa
A pupa ( la, pupa, "doll"; plural: ''pupae'') is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in thei ...
, which has seven moveable abdominal segments, all except the front one of which bears a band of setae. The posterior end of the pupa bears a group of spine-like tubercles.
Some species, such as deer flies and the Australian March flies, are known for being extremely noisy during flight, though clegs, for example, fly quietly and bite with little warning. Tabanids are agile fliers; '' Hybomitra'' species have been observed to perform aerial manoeuvres similar to those performed by fighter jets, such as the Immelmann turn
The term Immelmann turn, named after German World War I Eindecker fighter ace Lieutnant Max Immelmann, refers to two different aircraft maneuvers. In World War I aerial combat, an Immelmann turn was a maneuver used after an attack on another a ...
. Horseflies can lay claim to being the fastest flying insects; the male ''Hybomitra hinei wrighti'' has been recorded reaching speeds of up to when pursuing a female.
Distribution and habitat
Horse-flies are found worldwide, except for the polar regions, but they are absent from some islands such as Greenland
Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an island country in North America that is part of the Kingdom of Denmark. It is located between the Arctic and Atlantic oceans, east of the Canadian Arctic Archipelago. Greenland i ...
, Iceland
Iceland ( is, Ísland; ) is a Nordic island country in the North Atlantic Ocean and in the Arctic Ocean. Iceland is the most sparsely populated country in Europe. Iceland's capital and largest city is Reykjavík, which (along with its s ...
, and Hawaii
Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only state ...
. The genera ''Tabanus'', ''Chrysops'', and ''Haematopota'' all occur in temperate, subtropical, and tropical locations, but ''Haematopota'' is absent from Australia and South America. Horse-flies mostly occur in warm areas with suitable moist locations for breeding, but also occupy a wide range of habitats from deserts to alpine meadows. They are found from sea level to at least .
Evolution and taxonomy
The oldest records of the family come from the Early Cretaceous, with the oldest record being '' Eotabanoid,'' known from wings found in the Berriasian
In the geological timescale, the Berriasian is an age/stage of the Early/Lower Cretaceous. It is the oldest subdivision in the entire Cretaceous. It has been taken to span the time between 145.0 ± 4.0 Ma and 139.8 ± 3.0 Ma (million years ago ...
(145-140 million years ago) Purbeck Group
The Purbeck Group is an Upper Jurassic to Lower Cretaceous lithostratigraphic group (a sequence of rock strata) in south-east England. The name is derived from the district known as the Isle of Purbeck in Dorset where the strata are exposed in ...
of England. Although the bloodsucking habit is associated with a long proboscis, a fossil insect that has elongated mouthparts is not necessarily a bloodsucker, as it may instead have fed on nectar. The ancestral tabanids may have co-evolved with the angiosperm plants on which they fed. With a necessity for high-protein food for egg production, the diet of early tabanomorphs was probably predatory, and from this, the bloodsucking habit may have evolved. In the Santana Formation
The Santana Group is a geologic group, formerly included as the middle part of the Araripe Group, in the Araripe Basin of northeastern Brazil. The group comprises the Crato, Ipubi and Romualdo Formations and is dated to the Aptian to Albian sta ...
in Brazil, no mammals have been found, so the fossil tabanids found there likely fed on reptiles. Cold bloodsucking probably preceded warm bloodsucking, but some dinosaur
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...
s are postulated to have been warm-blooded and may have been early hosts for the horse-flies.
The Tabanidae are true flies
Flies are insects of the order Diptera, the name being derived from the Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced ...
and members of the insect
Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three ...
order Diptera. With the families Athericidae
Athericidae is a small family of flies known as water snipe flies or ibis flies. They used to be placed in the family Rhagionidae, but were removed by Stuckenberg in 1973. They are now known to be more closely related to Tabanidae. Species of At ...
, Pelecorhynchidae and Oreoleptidae, Tabanidae are classified in the superfamily Tabanoidea. Along with the Rhagionoidea, this superfamily makes up the infraorder Tabanomorpha
The Brachyceran infraorder Tabanomorpha is a small group that consists primarily of two large families, the Tabanidae (horse and deer flies) and Rhagionidae (snipe flies), and an assortment of very small affiliated families, most of which have b ...
. Tabanoid families seem to be united by the presence of a venom canal in the mandible of the larvae. Worldwide, about 4,455 species of Tabanidae have been described, over 1,300 of them in the genus ''Tabanus
''Tabanus'' is a genus of biting horseflies of the family Tabanidae. Females have scissor-like mouthparts that aim to cut the skin. The horsefly can then lap up the blood. Horseflies of this genus are known to be potential vectors of anthrax, ...
''.
Tabanid identification is based mostly on adult morphological characters of the head, wing venation, and sometimes the last abdominal segment. The genitalia are very simple and do not provide clear species differentiation as in many other insect groups. In the past, most taxonomic treatments considered the family to be composed of three subfamilies: Pangoniinae (tribes Pangoniini, Philolichini, Scionini), Chrysopsinae (tribes Bouvieromyiini, Chrysopsini, Rhinomyzini), and Tabaninae (tribes Diachlorini, Haematopotini, Tabanini). Some treatments increased this to five subfamilies, adding the subfamily Adersiinae, with the single genus ''Adersia
''Adersia'' is a genus of horseflies of the family Horse-fly, Tabanidae. It is the only genus in the tribe Adersiini, and the only member of the subfamily Adersiinae.
Species
*''Adersia ambigua'' Harold Oldroyd, Oldroyd, 1957
*''Adersia callani' ...
'', and the subfamily Scepcidinae, with the two genera '' Braunsiomyia'' and ''Scepsis
Scepsis or Skepsis ( grc, Σκῆψις or Σκέψις) was an ancient settlement in the Troad, Asia Minor that is at the present site of the village of Kurşunlutepe, near the town of Bayramiç in Turkey. The settlement is notable for being t ...
''.
A 2015 study by Morita et al. using nucleotide data, aimed to clarify the phylogeny
A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological spe ...
of the Tabanidae and supports three subfamilies. The subfamilies Pangoniinae and Tabaninae were shown to be monophyletic. The tribes Philolichini, Chrysopsini, Rhinomyzini, and Haematopotini were found to be monophyletic, with the Scionini also being monophyletic apart from the difficult-to-place genus ''Goniops''. ''Adersia'' was recovered within the Pangoniini as were the genera previously placed in the Scepcidinae, and ''Mycteromyia'' and ''Goniops'' were recovered within the Chrysopsini.
*Subfamily Chrysopsinae
Chrysopsinae is a subfamily of deer flies in the family Tabanidae.
Genera
These 33 genera belong to the subfamily Chrysopsinae:
*'' Aegophagamyia'' Austen, 1912
*'' Alocella'' Quentin, 1990
*'' Betrequia'' Oldroyd, 1970
*''Chrysops'' Meige ...
(deer flies or banded horse-flies)
*Subfamily Pangoniinae
Pangoniinae is a subfamily of Horse-flies in the order Diptera, containing at least four tribes and 24 genera.
Insects in this subfamily are distinguished from other Tabanidae by possession of ocelli and the antennal flagellum usually has eigh ...
(long-tongued horse-flies)
*Subfamily Tabaninae
Tabaninae is a subfamily of horse flies in the family Tabanidae. There are more than 3000 described species in Tabaninae.
Tribes and genera Diachlorini
*'' Acanthocera'' Macquart, 1834
*'' Acellomyia'' Gonzalez, 1999
*'' Anacimas'' Enderlei ...
(horse-flies)
The Tabaninae lack ocelli
A simple eye (sometimes called a pigment pit) refers to a form of eye or an optical arrangement composed of a single lens and without an elaborate retina such as occurs in most vertebrates. In this sense "simple eye" is distinct from a multi-l ...
(simple eyes) and have no spurs on the tips of their hind tibia
The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connects ...
e. In the Pangoniinae, ocelli are present and the antennal flagellum
A flagellum (; ) is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates.
A microorganism may have f ...
(whip-like structure) usually has eight annuli (or rings). In the Chrysopsinae, the antennal flagellum has a basal plate and the flagellum has four annuli. Females have a shining callus on the frons (front of the head between the eyes). The Adersiinae have a divided tergite on the ninth abdominal segment, and the Scepsidinae have highly reduced mouthparts. Members of the family Pelecorhynchidae were initially included in the Tabanidae and moved into the Rhagionidae
Rhagionidae or snipe flies are a small family of flies.
They get their name from the similarity of their often prominent proboscis that looks like the beak of a snipe.
Description
Rhagionidae are medium-sized to large flies with slender bodies a ...
before being elevated into a separate family. The infraorder
Order ( la, ordo) is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and ...
Tabanomorpha
The Brachyceran infraorder Tabanomorpha is a small group that consists primarily of two large families, the Tabanidae (horse and deer flies) and Rhagionidae (snipe flies), and an assortment of very small affiliated families, most of which have b ...
shares the blood-feeding habit as a common primitive characteristic, although this is restricted to the female.
Two well-known genera are the common horse-flies, ''Tabanus'', named by Swedish taxonomist
In biology, taxonomy () is the scientific study of naming, defining ( circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grouped into taxa (singular: taxon) and these groups are give ...
Carl Linnaeus
Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his Nobility#Ennoblement, ennoblement in 1761 as Carl von Linné#Blunt, Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalise ...
in 1758, and the deer flies, ''Chrysops'', named by the German entomologist Johann Wilhelm Meigen
Johann Wilhelm Meigen (3 May 1764 – 11 July 1845) was a German entomologist famous for his pioneering work on Diptera.
Life
Early years
Meigen was born in Solingen, the fifth of eight children of Johann Clemens Meigen and Sibylla Margareth ...
in 1802. Meigen did pioneering research on flies and was the author of ''Die Fliegen'' (''The Flies''); he gave the name ''Haematopota
''Haematopota'' is a genus of fly, flies in the horse-fly family, Tabanidae. Among the horse-flies, they are most commonly known as clegs. Many species have colorful, sinuously patterned eyes in life, a character that fades after death. The wings ...
'', meaning "blood-drinker", to another common genus of horse-flies.
Biology
Diet and biting behavior
Adult horse-flies feed on nectar and plant exudates, and some are important pollinators of certain specialised flowers;[ several South African and Asian species in the Pangoniinae have spectacularly long probosces adapted for the extraction of nectar from flowers with long, narrow corolla tubes, such as '']Lapeirousia
''Lapeirousia'' is a genus in the plant family Iridaceae. It is endemic to sub-Saharan Africa, about a third of the species occurring in fynbos.
Origin of the generic name
The genus ''Lapeirousia'' was described by Pierre André Pourret in Mé ...
'', and certain '' Pelargonium''.
Both males and females engage in nectar-feeding, but females of most species are anautogenous
In entomology, anautogeny is a reproductive strategy in which an adult female insect must eat a particular sort of meal (generally vertebrate blood) before laying eggs in order for her eggs to mature. This behavior is most common among dipteran ...
, meaning they require a blood meal before they are able to reproduce effectively. To obtain the blood, the females, but not the males, bite animals, including humans. The female needs about six days to fully digest her blood meal and after that, she needs to find another host. The flies seem to be attracted to a potential victim by its movement, warmth, and surface texture, and by the carbon dioxide
Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...
it breathes out. The flies mainly choose large mammals such as cattle, horses, camels, and deer, but few are species-specific. They have also been observed feeding on smaller mammals, birds, lizards, and turtles, and even on animals that have recently died.[ Unlike many biting insects such as ]mosquito
Mosquitoes (or mosquitos) are members of a group of almost 3,600 species of small flies within the family Culicidae (from the Latin ''culex'' meaning " gnat"). The word "mosquito" (formed by ''mosca'' and diminutive ''-ito'') is Spanish for "li ...
es, whose biting mechanism and saliva allow a bite not noticed by the host at the time, horse-fly bites are immediately irritating to the victim, so that they are often brushed off, and may have to visit multiple hosts to obtain sufficient blood. This behaviour means that they may carry disease-causing organisms from one host to another.[ The large animals and livestock mostly bitten by horse-flies are generally powerless to dislodge the fly, so there is no selective advantage for the flies to evolve a less immediately painful bite.
]
The mouthparts of females are of the usual dipteran form and consist of a bundle of six chitinous stylets that, together with a fold of the fleshy labium, form the proboscis
A proboscis () is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular mouthparts used for feeding and sucking. In vertebrates, a proboscis is an elong ...
. On either side of these are two maxillary palps. When the insect lands on an animal, it grips the surface with its clawed feet, the labium is retracted, the head is thrust downwards and the stylets slice into the flesh. Some of these have sawing edges and muscles can move them from side-to-side to enlarge the wound. Saliva containing anticoagulant is injected into the wound to prevent clotting.[ The blood that flows from the wound is lapped up by another mouthpart which functions as a sponge.] Horse-fly bites can be painful for a day or more; fly saliva may provoke allergic reactions such as hives and difficulty with breathing.[ Tabanid bites can make life outdoors unpleasant for humans, and can reduce milk output in cattle.][ They are attracted by polarized reflections from water, making them a particular nuisance near swimming pools. Since tabanids prefer to be in sunshine, they normally avoid shaded places such as barns, and are inactive at night.][
Attack patterns vary with species; clegs fly silently and prefer to bite humans on the wrist or bare leg; large species of ''Tabanus'' 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 note.] The striped hides of zebra
Zebras (, ) (subgenus ''Hippotigris'') are African equines with distinctive black-and-white striped coats. There are three living species: the Grévy's zebra (''Equus grevyi''), plains zebra (''E. quagga''), and the mountain zebra (''E. zebr ...
s may have evolved to reduce their attractiveness to horse-flies and tsetse flies
Tsetse ( , or ) (sometimes spelled tzetze; also known as tik-tik flies), are large, biting flies that inhabit much of tropical Africa. Tsetse flies include all the species in the genus ''Glossina'', which are placed in their own family, Glos ...
. The closer together the stripes, the fewer flies are visually attracted; the zebra's legs have particularly fine striping, and this is the shaded part of the body that is most likely to be bitten in other, unstriped equids. More recent research by the same lead author shows that the stripes were no less attractive to tabanids, but they merely touched—and could not make a controlled landing to bite. This suggests that a function of the stripes was interfering with optic flow.
This does not preclude the possible use of stripes for other purposes such as signaling or camouflage
Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard's spotted coat, the b ...
. Another disruptive mechanism may also be in play, however: a study comparing horse-fly behaviour when approaching horses wearing either striped or check-patterned rugs, when compared with plain rugs, found that both patterns were equally effective in deterring the insects.
Predators and parasites
The eggs of horse-flies are often attacked by tiny parasitic wasp
Parasitoid wasps are a large group of hymenopteran superfamilies, with all but the wood wasps (Orussoidea) being in the wasp-waisted Apocrita. As parasitoids, they lay their eggs on or in the bodies of other arthropods, sooner or later causi ...
s, and the larvae are consumed by birds, as well as being paratised by tachinid flies
The Tachinidae are a large and variable family of true flies within the insect order Diptera, with more than 8,200 known species and many more to be discovered. Over 1,300 species have been described in North America alone. Insects in this family ...
, fungi, and nematodes. Adult horse-flies are eaten by generalized predators such as birds, and some specialist predators, such as the horse guard wasp (a bembicinid wasp), also preferentially attack horse-flies, catching them to provision their nests.
Reproduction
Mating often occurs in swarms, generally at landmarks such as hilltops. The season, time of day, and type of landmark used for mating swarms are specific to particular species.
Egg
An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the a ...
s are laid on stones or vegetation near water, in clusters of up to 1000, especially on emergent water plants. The eggs are white at first but darken with age. They hatch after about six days, with the emerging larvae using a special hatching spike to open the egg case. The larva
A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle.
...
e fall into the water or onto the moist ground below. ''Chrysops'' species develop in particularly wet locations, while ''Tabanus'' species prefer drier places. The larvae are legless grubs, tapering at both ends. They have small heads and 11 or 13 segments and moult six to 13 times over the course of a year or more. In temperate species, the larvae have a quiescent period during winter (diapause), while tropical species breed several times a year. In the majority of species, they are white, but in some, they are greenish or brownish, and they often have dark bands on each segment. A respiratory siphon at the hind end allows the larvae to obtain air when submerged in water. Larvae of nearly all species are carnivorous, often cannibalistic in captivity, and consume worm
Worms are many different distantly related bilateral animals that typically have a long cylindrical tube-like body, no limbs, and no eyes (though not always).
Worms vary in size from microscopic to over in length for marine polychaete wo ...
s, insect larvae, and arthropod
Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chiti ...
s. The larvae may be parasitized by nematodes, flies of the families Bombyliidae and Tachinidae, and Hymenoptera in the family Pteromalidae. When fully developed, the larvae move into drier soil near the surface of the ground to pupa
A pupa ( la, pupa, "doll"; plural: ''pupae'') is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in thei ...
te.[
The pupae are brown and glossy, rounded at the head end, and tapering at the other end. Wing and limb buds can be seen and each abdominal segment is fringed with short spines. After about two weeks, metamorphosis is complete, the pupal case splits along the thorax, and the adult fly emerges. Males usually appear first, but when both sexes have emerged, mating takes place, courtship starting in the air and finishing on the ground. The female needs to feed on blood before depositing her egg mass.][
]
As disease vectors
Tabanids are known vectors for some blood-borne bacterial, viral, protozoan, and worm
Worms are many different distantly related bilateral animals that typically have a long cylindrical tube-like body, no limbs, and no eyes (though not always).
Worms vary in size from microscopic to over in length for marine polychaete wo ...
diseases of mammals, such as the equine infectious anaemia virus and various species of ''Trypanosoma
''Trypanosoma'' is a genus of kinetoplastids (class Trypanosomatidae), a monophyletic group of unicellular parasitic flagellate protozoa. Trypanosoma is part of the phylum Sarcomastigophora. The name is derived from the Greek ''trypano-'' ( ...
'' which cause diseases in animals and humans.[ Species of the genus '']Chrysops
Deer flies (also known in some parts of the mid-Atlantic United States as sheep flies) are bloodsucking insects considered pests to humans and cattle. They are large flies with large brightly-coloured compound eyes, and large clear wings with da ...
'' transmit the parasitic
Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...
filarial worm ''Loa loa
''Loa loa'' is a filarial (arthropod-borne) nematode (roundworm) that causes ''Loa loa'' filariasis. ''Loa loa'' actually means "worm worm", but is commonly known as the "eye worm", as it localizes to the conjunctiva of the eye. ''Loa loa'' is ...
'' between humans, and tabanids are known to transmit anthrax among cattle and sheep, and tularemia
Tularemia, also known as rabbit fever, is an infectious disease caused by the bacterium ''Francisella tularensis''. Symptoms may include fever, skin ulcers, and enlarged lymph nodes. Occasionally, a form that results in pneumonia or a throat infe ...
between rabbits and humans.
Blood loss is a common problem in some animals when large flies are abundant. Some animals have been known to lose up to of blood in a single day to tabanid flies, a loss which can weaken or even kill them. Anecdotal reports of horse-fly bites leading to fatal anaphylaxis
Anaphylaxis is a serious, potentially fatal allergic reaction and medical emergency that is rapid in onset and requires immediate medical attention regardless of use of emergency medication on site. It typically causes more than one of the foll ...
in humans have been made, an extremely rare occurrence.
Management
Controlling horse-flies is difficult. Malaise traps are most often used to capture them, and these can be modified with the use of baits and attractants that include carbon dioxide or octenol. A dark shiny ball suspended below them that moves in the breeze can also attract them and forms a key part of a modified "Manitoba trap" that is used most often for trapping and sampling the Tabanidae. Cattle can be treated with pour-on pyrethroid
A pyrethroid is an organic compound similar to the natural pyrethrins, which are produced by the flowers of pyrethrums (''Chrysanthemum cinerariaefolium'' and '' C. coccineum''). Pyrethroids are used as commercial and household insecticides.
I ...
s which may repel the flies, and fitting them with insecticide-impregnated eartags or collars has had some success in killing the insects.[
]
Horse-fly bites
Horse-fly bites can be painful to humans. Usually, a weal (raised area of skin) occurs around the site; other symptoms may include urticaria
Hives, also known as urticaria, is a kind of skin rash with red, raised, itchy bumps. Hives may burn or sting. The patches of rash may appear on different body parts, with variable duration from minutes to days, and does not leave any long-last ...
(a rash), dizziness, weakness, wheezing, and angioedema
Angioedema is an area of swelling (edema) of the lower layer of skin and tissue just under the skin or mucous membranes. The swelling may occur in the face, tongue, larynx, abdomen, or arms and legs. Often it is associated with hives, which are ...
(a temporary itchy, pink or red swelling occurring around the eyes or lips). A few people experience an allergic reaction. The National Health Service
The National Health Service (NHS) is the umbrella term for the publicly funded healthcare systems of the United Kingdom (UK). Since 1948, they have been funded out of general taxation. There are three systems which are referred to using the " ...
of the United Kingdom recommends that the site of the bite should be washed and a cold compress applied. Scratching the wound should be avoided at all times and an antihistamine
Antihistamines are drugs which treat allergic rhinitis, common cold, influenza, and other allergies. Typically, people take antihistamines as an inexpensive, generic (not patented) drug that can be bought without a prescription and provid ...
preparation can be applied. In most cases, the symptoms subside within a few hours, but if the wound becomes infected, medical advice should be sought.
In literature
In ''Prometheus Bound
''Prometheus Bound'' ( grc, Προμηθεὺς Δεσμώτης, ''Promētheús Desmṓtēs'') is an Ancient Greek tragedy traditionally attributed to Aeschylus and thought to have been composed sometime between 479 BC and the terminus ant ...
'', which is attributed to the Athenian tragic playwright Aeschylus
Aeschylus (, ; grc-gre, Αἰσχύλος ; c. 525/524 – c. 456/455 BC) was an ancient Greek tragedian, and is often described as the father of tragedy. Academic knowledge of the genre begins with his work, and understanding of earlier Greek ...
, a gadfly sent by Zeus
Zeus or , , ; grc, Δῐός, ''Diós'', label= genitive Boeotian Aeolic and Laconian grc-dor, Δεύς, Deús ; grc, Δέος, ''Déos'', label= genitive el, Δίας, ''Días'' () is the sky and thunder god in ancient Greek reli ...
's wife Hera pursues and torments his mistress Io, who has been transformed into a cow and is watched constantly by the hundred eyes of the herdsman Argus: "Io: Ah! Hah! Again the prick, the stab of gadfly-sting! O earth, earth, hide, the hollow shape—Argus—that evil thing—the hundred-eyed." William Shakespeare
William Shakespeare ( 26 April 1564 – 23 April 1616) was an English playwright, poet and actor. He is widely regarded as the greatest writer in the English language and the world's pre-eminent dramatist. He is often called England's nation ...
, inspired by Aeschylus, has Tom o' Bedlam
"Tom o' Bedlam" is the title of an anonymous poem in the "mad song" genre, written in the voice of a homeless " Bedlamite". The poem was probably composed at the beginning of the 17th century. In ''How to Read and Why'' Harold Bloom called it "the ...
in ''King Lear
''King Lear'' is a tragedy written by William Shakespeare.
It is based on the mythological Leir of Britain. King Lear, in preparation for his old age, divides his power and land between two of his daughters. He becomes destitute and insane ...
'', "Whom the foul fiend hath led through fire and through flame, through ford and whirlpool, o'er bog and quagmire", driven mad by the constant pursuit. In '' Antony and Cleopatra'', Shakespeare likens Cleopatra's hasty departure from the Actium battlefield to that of a cow chased by a gadfly: "The breeze adfly
URL shortening is a technique on the World Wide Web in which a Uniform Resource Locator (URL) may be made substantially shorter and still direct to the required page. This is achieved by using a redirect which links to the web page that has a ...
upon her, like a cow in June / hoists sail and flies", where "June" may allude not only to the month but also to the goddess Juno
Juno commonly refers to:
*Juno (mythology), the Roman goddess of marriage and queen of the gods
*Juno (film), ''Juno'' (film), 2007
Juno may also refer to:
Arts, entertainment and media Fictional characters
*Juno, in the film ''Jenny, Juno''
*Ju ...
, who torments Io, and the cow in turn may allude to Io, who is changed into a cow in Ovid
Pūblius Ovidius Nāsō (; 20 March 43 BC – 17/18 AD), known in English as Ovid ( ), was a Roman poet who lived during the reign of Augustus. He was a contemporary of the older Virgil and Horace, with whom he is often ranked as one of the th ...
's ''Metamorphoses
The ''Metamorphoses'' ( la, Metamorphōsēs, from grc, μεταμορφώσεις: "Transformations") is a Latin narrative poem from 8 CE by the Roman poet Ovid. It is considered his ''magnum opus''. The poem chronicles the history of the ...
''.
The physician and naturalist Thomas Muffet
Thomas Muffet (also Moufet, Mouffet, or Moffet) (1553 – 5 June 1604) was an English naturalist and physician. He is best known his study of insects and arthropods in regard to medicine (particularly spiders), his support of the Paracelsian sy ...
wrote that the horse-fly "carries before him a very hard, stiff, and well-compacted sting, with which he strikes through the Oxe his hide; he is in fashion like a great Fly, and forces the beasts for fear of him only to stand up to the belly in water, or else to betake themselves to wood sides, cool shades, and places where the wind blows through." The " Blue Tail Fly" in the eponymous song was probably the mourning horsefly (''Tabanus atratus
''Tabanus'' is a genus of biting horseflies of the family Tabanidae. Females have scissor-like mouthparts that aim to cut the skin. The horsefly can then lap up the blood. Horseflies of this genus are known to be potential vectors of anthrax ...
''), a tabanid with a blue-black abdomen common to the southeastern United States.[
]Paul Muldoon
Paul Muldoon (born 20 June 1951) is an Irish poet. He has published more than thirty collections and won a Pulitzer Prize for Poetry and the T. S. Eliot Prize. At Princeton University he is currently both the Howard G. B. Clark '21 University P ...
’s chapbook Binge contains a poem “Clegs and Midges” which uses gadflies, real and metaphoric, “cleg” being a British term for the horse-fly.
In Norse mythology Loki took the form of a gadfly to hinder Brokkr
In Norse mythology, Brokkr (Old Norse: , "the one who works with metal fragments; blacksmith", anglicized Brokk) is a dwarf, and the brother of Eitri or Sindri.
According to ''Skáldskaparmál'', Loki had Sif's hair, Freyr's ship Skíðblaðn ...
during the manufacture of the hammer Mjölnir
Mjölnir (from Old Norse Mjǫllnir) is the hammer of the thunder god Thor in Norse mythology, used both as a devastating weapon and as a divine instrument to provide blessings. The hammer is attested in numerous sources, including the 11th cen ...
, weapon of Thor
Thor (; from non, Þórr ) is a prominent god in Germanic paganism. In Norse mythology, he is a hammer-wielding god associated with lightning, thunder, storms, sacred groves and trees, strength, the protection of humankind, hallowing, an ...
(Hammer of Thor).
See also
*List of soldierflies and allies of Great Britain
The following is a list of the larger Brachycera recorded in Britain, this includes the soldierflies and their allies.
Family Xylophagidae
* '' Xylophagus ater'' - common awl-fly
* '' Xylophagus cinctus'' - red-belted awl-fly
* '' Xylophagus j ...
*Use of DNA in forensic entomology
Forensic entomology has three sub-fields: urban, stored product and medico-criminal entomologies. This article focuses on medico-criminal entomology and how DNA is analyzed with various blood-feeding insects.
Forensic entomology can be an import ...
References
External links
*
*
{{DEFAULTSORT:Horse-Fly
Extant Late Jurassic first appearances
Insects in culture
Flies and humans