View source for Tabanidae

{{redirect|Horsefly}}
{{featured article}}
{{Automatic Taxobox
| image             = Horse fly Tabanus 2.jpg
| image_caption     =  ''Tabanus sulcifrons''<ref>Cirrus Digital [http://www.cirrusimage.com/fly_horse_Tabanus.htm Horse Fly ''Tabanus sulcifrons'']</ref>
| taxon             = Tabanidae
| authority         = [[Pierre André Latreille|Latreille]], 1802<ref name="Nomenclature1961">{{cite book |author=International Commission on Zoological Nomenclature |title=The Bulletin of Zoological Nomenclature |url=https://books.google.com/books?id=XxoTAAAAIAAJ |year=1961 |publisher=International Trust for Zoological Nomenclature |page=55}}</ref>
| subdivision_ranks = [[Genus|Genera]]
| subdivision = 
Subfamily [[Chrysopsinae]]:<br>
*''[[Merycomyia]]''
*''[[Deer Fly|Chrysops]]''
*''[[Horse fly|Neochrysops]]''
*''[[Silvius (insect)|Silvius]]''
Subfamily [[Pangoniinae]]:<br>
*''[[Apatolestes]]''
*''[[Asaphomyia]]''
*''[[Brennania]]''
*''[[Esenbeckia (fly)|Esenbeckia]]''
*''[[Zimb|Pangonia]]''
*''[[Pegasomyia]]''
*''[[Stonemyia]]''
*''[[Goniops]]''
Subfamily [[Tabaninae]]:<br>
*''[[Anacimas]]''
*''[[Bolbodimyia]]''
*''[[Catachlorops]]''
*''[[Chlorotabanus]]''
*''[[Diachlorus]]''
*''[[Dichelacera]]''
*''[[Holcopsis]]''
*''[[Lepiselaga]]''
*''[[Leucotabanus]]''
*''[[Microtabanus]]''
*''[[Stenotabanus]]''
*''[[Haematopota]]''
*''[[Agkistrocerus]]''
*''[[Atylotus]]''
*''[[Hamatabanus]]''
*''[[Hybomitra]]''
*''[[Poeciloderas]]''
*''[[Tabanus]]''
*''[[Therioplectes]]''
*''[[Whitneyomyia]]''
}}
'''Horse-flies''' or '''horseflies''' (for other names, see [[Horse-fly#Common names|common names]]) are true [[Fly|flies]] in the family '''Tabanidae''' in the [[insect]] [[Order (biology)|order]] [[Diptera]]. They are often large and agile in flight, and the females 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.  Horse-flies are sometimes also referred to as '''gadflies''', though this term is ambiguous and often refers instead to [[Botfly|botflies]] (Oestridae).

Adult horse-flies feed on nectar and plant exudates; the males have weak [[insect mouthparts|mouthparts]] and only the females bite animals to obtain enough [[protein]] from blood to produce [[egg]]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 and grow in semiaquatic habitats.

Female horse-flies can [[vector (epidemiology)|transfer]] [[blood-borne disease]]s from one animal to another through their feeding habit. In areas where diseases occur, they have been known to carry [[equine infectious anemia|equine infectious anaemia virus]], some [[Trypanosoma|trypanosomes]], the [[filariasis|filarial worm]] ''[[Loa loa]]'', [[anthrax]] among cattle and sheep, and [[tularemia]]. As well as making life outdoors uncomfortable for humans, 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]] in [[Ancient Greece]] mentioned them driving people to madness through their persistent pursuit. [[Shakespeare]] uses the theme of the maddening gadfly in his plays ''[[King Lear]]'' and ''[[Antony and Cleopatra]]''.

==Common names==
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[g]", "gleg" or "clag", which comes from [[Old Norse]] and may have originated from the [[Vikings]].<ref name=Marren/> 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 [[Red deer|deer]] roam,<ref name=Marren/> and "buffalo-flies", "moose-flies" and "elephant-flies" emanate from other parts of the world where these animals are found.<ref name=chainey1993/> In North America they are known as "breeze-flies",<ref>{{cite book|author1=Cooke, Mordecai Cubitt |author2=Taylor, John Eller |title=Hardwicke's Science-gossip: An Illustrated Medium of Interchange and Gossip for Students and Lovers of Nature |url=https://books.google.com/books?id=JjNKAQAAMAAJ&pg=PA194 |year=1866 |publisher=Robert Hardwicke |page=194}}</ref> and in Australia, some are known as "March flies",<ref>{{cite web |url=http://medent.usyd.edu.au/fact/biting%20flies.htm |title=Biting flies |author=Doggett, Stephen L. |date=20 January 2010 |publisher=University of Sydney and Westmead Hospital: Department of Medical Entomology |accessdate=30 July 2015}}</ref> a name used in other Anglophonic countries to refer to the non-bloodsucking [[Bibionidae]].<ref>{{cite web |url=http://bugguide.net/node/view/3834 |title=Family Bibionidae: March Flies |publisher=Iowa State University |work=BugGuide |accessdate=30 July 2015}}</ref>

==Description==
[[File:Tabanus atratus, U, Face, MD 2013-08-21-16.06.31 ZS PMax (9599360121).jpg|thumb|left|Head of ''[[Tabanus atratus]]'' showing large compound eyes, short antennae (between and below the eyes) and stout piercing mouthparts]]

Adult tabanids are large flies with prominent [[Eye#Compound eyes|compound eyes]], short [[Antenna (biology)|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 (insect anatomy)|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]]. 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.<ref name=chainey1993>{{cite book |author=Chainey, John E. |chapter=Horse-flies, deer-flies and clegs (Tabanidae) |title=Medical Insects and Arachnids |editors=Lane, R.P.; Crosskey,  R.W. |year=1993 |publisher=Springer |url=https://link.springer.com/chapter/10.1007/978-94-011-1554-4_8 |isbn=978-94-011-1554-4 |pages=310–332|doi=10.1007/978-94-011-1554-4_8 }}</ref> Species recognition is based on details of head structures (antennae, [[Insect morphology#Head|frons]], and [[Maxilla (arthropod mouthpart)|maxillae]]), 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.<ref name=chainey1993/>

Tabanid species range from medium-sized to very large, robust insects. Most have a body length between {{convert|5|and|25|mm|in|1|abbr=on}}, with the largest having a wingspan of {{convert|60|mm|in|1|abbr=on}}.<ref name=Cook>{{cite book |author1=Cook, Gordon Charles |author2=Zumla, Alimuddin |title=Manson's Tropical Diseases |url=https://books.google.com/books?id=CF2INI0O6l0C&pg=PA1752 |year=2009 |publisher=Elsevier |isbn=1-4160-4470-1 |page=1752}}</ref> Deer flies in the genus ''[[Deer fly|Chrysops]]'' are up to {{convert|10|mm|in|1|abbr=on}} long, have yellow to black bodies and striped abdomens, and membranous wings with dark patches. Horse-flies (genus ''[[Tabanus]]'') are larger, up to {{convert|25|mm|in|0|abbr=on}} 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.<ref name=IFAS>{{cite web |url=http://entnemdept.ufl.edu/creatures/livestock/deer_fly.htm |title=Deer flies, yellow flies and horse flies |author=Squitier, Jason M. |date=1 April 2014 |work=Featured Creatures |publisher=University of Florida |accessdate=24 July 2015}}</ref> Some species in the subfamily Pangoniinae have an exceptionally long [[proboscis]] (tubular mouthpart).<ref name=chainey1993 />

The larvae are long and cylindrical with small heads and 12 body segments. They have rings of [[Tubercle (anatomy)|tubercle]]s (warty outgrowths) known as pseudopods around the segments, and also bands of short [[seta]]e (bristles). The posterior tip of each [[larva]] 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]], 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.<ref name=Walker>{{cite book |author=Walker, A.R. |title=Arthropods of Humans and Domestic Animals: A Guide to Preliminary Identification |url=https://books.google.com/books?id=WKMeTbKOBuIC&pg=PA78 |year=1994 |publisher=Springer Science & Business Media |isbn=978-0-412-57280-7 |pages=78–79}}</ref>

[[File:Hevoset kesälaitumella 10.jpg|thumb|upright|Horse-flies ''[[Haematopota pluvialis]]'' feeding on a horse's head]]

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]].<ref>{{cite journal |author1=Wilkerson, R.C. |author2=Butler, J.F. |year=1984 |title=The Immelman turn, a pursuit maneuver used by hovering male ''Hybomitra hinei wrighti'' (Diptera: Tabanidae |journal=Annals of the Entomological Society of America |volume=77 |issue=3 |pages=293–295 |doi=10.1093/aesa/77.3.293}}</ref>

==Distribution and habitat==
Horse-flies are found worldwide, except for the polar regions, but they are absent from some islands such as [[Greenland]], [[Iceland]], and [[Hawaii (island)|Hawaii]].<ref name=IFAS/> The genera ''Tabanus'', ''Chrysops'', and ''Haematopota'' all occur in temperate, subtropical, and tropical locations, but ''Haematopota'' is absent from Australia and South America.<ref name=Cook/> 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 {{convert|3300|m|ft|-2|abbr=on}}.<ref name=Middlekauff>{{cite book |author1=Middlekauff, Woodrow Wilson |author2=Lane, Robert S. |title=Adult and Immature Tabanidae (Diptera) of California |url=https://books.google.com/books?id=RSGsDQg7nDQC&pg=PA1 |year=1980 |publisher=University of California Press |isbn=978-0-520-09604-2 |pages=1–2}}</ref>

==Evolution and taxonomy==
The first record of a tabanid comes from the [[Late Jurassic]] of China, and specimens from the [[Cretaceous]] have been found in England, Spain, and possibly South Africa. In the New World, the first discoveries date from the [[Miocene]] of [[Florissant, Colorado]]. These insects are recognisable as tabanids both from their mouthparts and their wing venation.<ref name=Martins>{{cite journal |author=Martins-Neto, Rafael Gioia |year=2003 |title=The fossil tabanids (Diptera Tabanidae): When they began to appreciate warm blood and when they began transmit diseases? |journal=Mem Inst Oswaldo Krubs |volume=98 |issue=1 |pages=29–34 |pmid=12687759 |url=http://www.scielo.br/pdf/mioc/v98s1/v98s1a06.pdf |doi=10.1590/s0074-02762003000900006}}</ref> 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.<ref name=Grimaldi2005>{{cite book |author1=Grimaldi, David |author2= Engel, Michael S. |title=Evolution of the Insects |url=https://books.google.com/books?id=odQmAAAAQBAJ&pg=PA522 |year=2005 |publisher=Cambridge University Press |isbn=978-1-107-26877-7 |pages=522–}}</ref> The ancestral tabanids may have co-evolved with the angiosperm plants on which they fed.<ref name=Morita/> 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]] 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]]s are postulated to have been warm-blooded and may have been early hosts for the horse-flies.<ref name=Martins/>

The Tabanidae are [[Fly|true flies]] and members of the [[insect]] [[Order (biology)|order]] Diptera.<ref>{{cite book |last1=Chvala |first1=M. |last2=Lyneborg |first2=L.|last3=Moucha |first3=J. |title=Horse Flies of Europe (Diptera, Tabanidae) |date=1972 |publisher=Entomological Society of Copenhagen |isbn=978-0-900848-57-5 |url=https://books.google.com/books/about/The_Horse_Flies_of_Europe.html?id=mCRDAAAAYAAJ}}</ref><ref>{{cite book |last1=Moucha |first1=J. |title=Horse-flies (Diptera: Tabanidae) of the World: Synoptic Catalogue |date=1976 |publisher=Národní muzeum – Přírodovědecké muzeum}}</ref> With the families [[Athericidae]], [[Pelecorhynchidae]] and [[Oreoleptidae]], te Tabanidae are classified in the [[Taxonomic rank#Ranks in zoology|superfamily]] [[Tabanoidea]]. Along with the Rhagionoidea, this superfamily makes up the infraorder [[Tabanomorpha]]. 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 [[Species description|described]], over 1,300 of them in the genus ''[[Tabanus]]''.<ref name=Morita/>

Tabanid identification is based mostly on adult [[Morphology (biology)|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).<ref name=chainey1993 /> Some treatments increased this to five subfamilies, adding the subfamily Adersiinae, with the single genus ''[[Adersia]]'', and the subfamily Scepcidinae, with the two genera ''[[Braunsiomyia]]'' and ''[[Scepsis (genus)|Scepsis]]''.<ref name=mackerras1>{{cite journal |author=Mackerras, I.M. |year=1954 |title=The classification and distribution of Tabanidae (Díptera). I. General review |journal= Australian Journal of Zoology|volume=2 |issue=3 |pages=431–454 |doi=10.1071/zo9540431}}</ref>

A 2015 study by Morita et al. using [[Nucleic acid sequence|nucleotide data]], aimed to clarify the [[Phylogenetics|phylogeny]] of the Tabanidae and supports three subfamilies. The subfamilies Pangoniinae and Tabaninae were shown to be [[Monophyly|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.<ref name=Morita>{{cite journal |author1=Morita, Shelah I. |author2=Bayless, Keith M. |author3=Yeates, David K. |author4=Wiegmann, Brian M. |year=2015 |title=Molecular phylogeny of the horse flies: a framework for renewing tabanid taxonomy |journal=Systematic Entomology |volume= 41|issue= |pages= 56|doi=10.1111/syen.12145 }}</ref>

[[File:Tabanidae - Chrysops caecutiens.JPG|thumb|upright|A deer fly, ''[[Chrysops caecutiens]]'']]
[[File:Tabanus eggeri.jpg|thumb|upright|A horse-fly, ''[[Tabanus eggeri]]'', France]]

*Subfamily [[Chrysopsinae]] (deer flies or banded horse-flies)
*Subfamily [[Pangoniinae]] (long-tongued horse-flies)
*Subfamily [[Tabaninae]] (horse-flies)

The Tabaninae lack [[Simple eye in invertebrates|ocelli]] (simple eyes) and have no spurs on the tips of their hind [[tibia]]e. In the Pangoniinae, ocelli are present and the antennal [[flagellum]] (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).<ref>{{cite book |title=The Insects of Australia. Volume 2. |edition=2 |publisher=CSIRO| pages= 754–755 |isbn=978-0-522-84638-6 |year=1991|author1=Colless, D.H.| author2=McAlpine, D.K.}}</ref> The Adersiinae have a divided tergite on the ninth abdominal segment,<ref>{{cite book |author=Mackerras, I.M. |title=The Classification and Distribution of Tabanidae (Diptera) |url=https://books.google.com/books?id=iS9DAAAAYAAJ |publisher=Cornell University |year=1954 |page=584}}</ref> and the Scepsidinae have highly reduced mouthparts.<ref>{{cite journal| title=The classification and distribution of Tabanidae (Diptera). III. Subfamilies Scepsidinae and Chrysopinae| year=1955| author=Mackerras, I.M.| journal=Australian Journal of Zoology| volume=3| issue=4| pages=583–633 |doi=10.1071/ZO9550583}}</ref> Members of the family [[Pelecorhynchidae]] were initially included in the Tabanidae and moved into the [[Rhagionidae]] before being elevated into a separate family. The [[infraorder]] [[Tabanomorpha]] shares the blood-feeding habit as a common primitive characteristic, although this is restricted to the female.<ref name=morita>{{cite journal |title=A phylogeny of long-tongued horse flies (Diptera:Tabanidae:Philoliche) with the first cladistic review of higher relationships within the family |last=Morita| first=Shelah I.| journal=Invertebrate Systematics| year=2008| volume=22|issue=3| pages=311–327 |doi=10.1071/IS07005 }}</ref>

Two well-known genera are the common horse-flies, ''Tabanus'', named by Swedish [[Taxonomy (biology)|taxonomist]] [[Carl Linnaeus]] in 1758, and the deer flies, ''Chrysops'', named by the German [[Entomology|entomologist]] [[Johann Wilhelm Meigen]] in 1802.<ref name=kaufman>{{Cite book| publisher=Hillstar Editions| isbn=0-618-15310-1| page=284| last=Eaton| first=Eric R.|author2=Kaufman, Kenn| title=Kaufman Field Guide to Insects of North America| chapter=Deer flies and horse flies| year=2007 |url=https://books.google.com/?id=aWVi0IF_jcQC&pg=PA284}}</ref> Meigen did pioneering research on flies and was the author of ''Die Fliegen'' (Flies); he gave the name ''[[Haematopota]]'', blood-drinker,<ref>{{cite book |author=Sherborn, C.D.| year=1850 | title=Index Animalum. H, I, J, K, L |publisher=Oxford University Press |url=https://archive.org/texts/flipbook/flippy.php?id=sil34_02_12| page=2889}}</ref> to another common genus of horse-flies.<ref name="MiddlekauffLane1980">{{cite book |last1=Middlekauff |first1=Woodrow Wilson |last2=Lane |first2=Robert S. |title=Adult and Immature Tabanidae (Diptera) of California |url=https://books.google.com/books?id=RSGsDQg7nDQC&pg=PA40 |year=1980 |publisher=University of California Press |isbn=978-0-520-09604-2 |page=40}}</ref>

==Biology==
===Diet and biting behavior===
Adult horse-flies feed on nectar and plant [[exudate]]s, and some are important [[pollinator]]s of certain specialised flowers;<ref name=Morita/> several [[South Africa]]n and Asian species in the Pangoniinae have spectacularly long probosces adapted for the extraction of nectar from flowers with long, narrow [[petal|corolla]] tubes, such as ''[[Lapeirousia]]'',<ref>{{cite journal |author1=Goldblatt, Peter |author2=Manning, John C. |author3=Bernhardt, Peter |year=1995 |title=Pollination biology of ''Lapeirousia'' subgenus ''Lapeirousia'' (Iridaceae) in southern Africa; floral divergence and adaptation for long-tongued fly pollination |journal=Annals of the Missouri Botanical Garden |volume=82 |issue=4 |pages=517–534 |doi=10.2307/2399833 }}</ref> and certain ''[[Pelargonium]]''.<ref>{{cite journal |author1=Combs, J.K. |author2=Pauw, A. |year=2009 |title=Preliminary evidence that the long-proboscid fly, ''Philoliche gulosa'', pollinates ''Disa karooica'' and its proposed Batesian model ''Pelargonium stipulaceum'' |journal=South African Journal of Botany |volume=75 |issue=4 |pages=757–761 |doi=10.1016/j.sajb.2009.06.015 }}</ref>

Both males and females engage in nectar feeding, but in addition to this, females of most species are [[Anautogeny|anautogenous]], meaning they require a blood meal before they are able to reproduce effectively. To obtain the blood, the females bite animals, including humans, while the males are harmless. The female needs about six days to fully digest her blood meal and after that, she needs to find another host.<ref name=Marren>{{cite book|author1=Marren, Peter |author2=Mabey, Richard |title=Bugs Britannica |url=https://books.google.com/books?id=Ah62bUZLDOwC&pg=PA312 |year=2010 |publisher=Chatto & Windus |isbn=978-0-7011-8180-2 |page=312}}</ref> The flies seem to be attracted to a potential victim by its movement, warmth, and surface texture, and by the [[carbon dioxide]] it breathes out.<ref name=Kentucky>{{cite web |title=Horse Flies and Deer Flies |url=http://www2.ca.uky.edu/entomology/entfacts/ef511.asp |publisher=University of Kentucky |accessdate=24 July 2015}}</ref> 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. Because their bite is irritating to the victim, 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.<ref name=Middlekauff/>

[[File:Tabanus-horsefly-mouthparts-2.jpg|thumb|left|''[[Tabanus]]'' mouthparts: The sharp cutting stylets are on the right, the spongelike lapping part in the centre.]]
The mouthparts of females are of the usual dipteran form and consist of a bundle of six [[chitin]]ous stylets that, together with a fold of the fleshy [[Labium (arthropod mouthpart)|labium]], form the [[proboscis]]. 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.<ref name=Kentucky/><ref>{{cite journal |title=Identification of anticoagulant activities in salivary gland extracts of four horsefly species (Diptera, Tabanidae) |author1=Kazimírová, M. |author2=Šulanová, M. |author3=Kozánek, M. |author4=Takáč, P. |author5=Labuda, M. |author6=Nuttall, P.A. |journal=Haemostasis |year=2001 |volume=31 |pages=294–305 |pmid=11910198 |doi=10.1159/000048076}}</ref><ref>{{cite web |url=http://www.microscopy-uk.org.uk/mag/artapr12/at-HorseFlyhead.pdf |title=Horse Fly head |author=Thomas, Anthony |date=1 April 2012 |work=Micscape Magazine |publisher=Microscopy-UK |accessdate=25 July 2015}}</ref> The blood that flows from the wound is lapped up by another mouthpart which functions as a sponge.<ref name=Purdue>{{cite web |title=Horse and Deer Flies |url=http://extension.entm.purdue.edu/publichealth/insects/tabanid.html |work=Medical Entomology |publisher=Purdue University |accessdate=24 July 2015}}</ref> 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 reflections from water which are polarized,<ref>{{cite journal| journal=Naturwissenschaften |year=2008 |volume=95 |issue=11| pages=1093–1100 |pmid=18685822 |doi=10.1007/s00114-008-0425-5| title=Ventral polarization vision in tabanids: horseflies and deerflies (Diptera: Tabanidae) are attracted to horizontally polarized light |author1=Horváth, G |author2=Majer, J |author3=Horváth, L |author4=Szivák, I |author5=Kriska, G.}}</ref> 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.<ref name=Kentucky/>

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.<ref name="MarrenMabey2010">{{cite book |last1=Marren |first1=Peter |last2=Mabey |first2=Richard |title=Bugs Britannica |url=https://books.google.com/books?id=Ah62bUZLDOwC&pg=PA312 |year=2010 |publisher=Chatto & Windus |isbn=978-0-7011-8180-2 |pages=310–312}}</ref> The striped hides of [[zebra]]s may have evolved to reduce their attractiveness to horse-flies and [[Tsetse fly|tsetse flies]] than either plain dark or plain white hides. 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.<ref>{{cite journal |author1=Caro, Tim |author2=Izzo, Amanda |author3=Reiner, Robert C. Jr |author4=Walker, Hannah |author5=Stankowich, Theodore |year=2014 |title=The function of zebra stripes |journal=Nature Communications |volume=5 |pages=3535 |doi=10.1038/ncomms4535 |pmid=24691390}}</ref>
This does not preclude the possible use of stripes for other purposes such as [[signaling theory|signaling]] or [[camouflage]].<ref>{{Cite journal | doi = 10.1242/jeb.065540| title = Polarotactic tabanids find striped patterns with brightness and/or polarization modulation least attractive: An advantage of zebra stripes| journal = Journal of Experimental Biology| volume = 215| issue = 5| pages = 736| year = 2012| last1 = Egri | first1 = A.| last2 = Blaho | first2 = M.| last3 = Kriska | first3 = G.| last4 = Farkas | first4 = R.| last5 = Gyurkovszky | first5 = M.| last6 = Akesson | first6 = S.| last7 = Horvath | first7 = G. | pmid=22323196}}</ref>

===Predators and parasites===
[[File:Horse guard wasp.jpg|thumb|The [[horse guard wasp]], ''Stictia carolina'', catches horse-flies to provision its nest.]]
The eggs of horse-flies are often attacked by tiny [[Parasitoid wasp|parasitic wasp]]s, and the larvae are consumed by birds, as well as being paratised by [[Tachinidae|tachinid flies]], fungi, and [[nematode]]s.<ref>{{cite book|title=Horseflies of the Guyana biology, veterinary significance & control methods|url=https://books.google.com/books?id=YYIqAAAAYAAJ&pg=PA11 |publisher=IICA Biblioteca Venezuela|pages=11–12 |id=GGKEY:5W9UT3G8BAF}}</ref> Adult horse-flies are eaten by generalized predators such as birds,<ref>{{cite journal|journal=Ornitologia Neotropical| volume=17| pages= 619–622|year=2006| title=Predation of hilltopping horse-flies (Tabanidae) by birds in Brazil|author1=Braga da Rosa |author2=Gustavo A. |url=https://sora.unm.edu/sites/default/files/journals/on/v017n04/p0619-p0622.pdf}}</ref> and some specialist predators, such as the [[horse guard wasp]] (a [[Bembicini|bembicinid wasp]]), also preferentially attack horse-flies, catching them to [[mass provisioning|provision their nests]].<ref name="Martin2013">{{cite book |last=Martin |first=Anthony J. |title=Life Traces of the Georgia Coast: Revealing the Unseen Lives of Plants and Animals |url=https://books.google.com/books?id=na3v39RVqFEC&pg=PA209 |year=2013 |publisher=Indiana University Press |isbn=0-253-00602-3 |pages=209–210}}</ref>

===Reproduction===
Mating often occurs in swarms, generally at landmarks such as [[Hill-topping (biology)|hilltops]]. The season, time of day, and type of landmark used for mating swarms are specific to particular species.<ref>{{cite journal |author1=Wilkerson, R.C. |author2=Butler, J.F. |author3=Pechuman, L.L. | date=1985 | title=Swarming, hovering and mating behavior of male horse flies and deer flies (Diptera: Tabanidae) | journal=Myia | volume=3 | pages=515–546}}</ref><ref>{{cite journal |title=Insect swarming and mating|author=Sullivan, Robert T.|journal=Florida Entomologist| volume=64 |issue=1| year=1981 |pages=44–65|url=http://ojs-test.fcla.edu/index.php/flaent/article/viewFile/57544/55223 |doi=10.2307/3494600}}</ref>

[[File:Horse Fly (Tabanidae) female laying eggs (12615749733).jpg|left|thumbnail|Female horse-fly laying eggs]]
[[Egg]]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]]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 [[Carnivore|carnivorous]], often cannibalistic in captivity, and consume [[worm]]s, insect larvae, and [[arthropod]]s. The larvae may be parasitized by nematodes, flies of the families Bombyliidae and Tachinidae, and Hymenoptera in the family [[Pteromalidae]].<ref name=chainey1993 /> When fully developed, the larvae move into drier soil near the surface of the ground to [[pupa]]te.<ref name=IFAS/>

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.<ref name=Marren/><ref name=IFAS/>

[[File:EuropäischenZweiflügeligen1790TafCXCIV.jpg|thumb|upright|[[Johann Wilhelm Meigen]]'s  ''Europäischen Zweiflügeligen'' 1790, Plate CXCIV. Nos 7, 8 and 9 are ''Haematopota'' horse-flies, ''H. crassicornis'', ''H. grandis'', and H. pluvialis'', respectively.]]

===As disease vectors===

Tabanids are known [[vector (epidemiology)|vectors]] for some [[blood-borne disease|blood-borne]] bacterial, viral, [[Protozoan infection|protozoan]], and [[Helminths|worm]] diseases of mammals, such as the [[equine infectious anemia|equine infectious anaemia virus]] and various species of ''[[Trypanosoma]]'' which cause diseases in animals and humans.<ref name=Cheng/> Species of the genus ''[[Chrysops]]'' transmit the [[parasitism|parasitic]] [[filariasis|filarial worm]] ''[[Loa loa]]'' between humans,<ref name=Padgett>{{cite journal |author1=Padgett, J.J. |author2=Jacobsen, K.H. |title=Loiasis: African eye worm |journal=Transactions of the Royal Society of Tropical Medicine and Hygiene |volume=102 |issue=10 |pages=983–9 |year=2008 |pmid=18466939 |doi=10.1016/j.trstmh.2008.03.022}}</ref> and tabanids are known to transmit [[anthrax]] among cattle and sheep, and [[tularemia]] between [[rabbit]]s and humans.<ref name=Cheng>{{cite book|author=Cheng, Thomas C.|title=General Parasitology |url=https://books.google.com/books?id=d4GQlYzode8C&pg=PA660 |year=2012 |publisher=Elsevier Science |isbn=978-0-323-14010-2 |page=660}}</ref>

Blood loss is a common problem in some animals when large flies are abundant. Some animals have been known to lose up to {{convert|300|ml|abbr=on}} 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]] in humans have been made, an extremely rare occurrence.<ref>{{cite journal |title=The wasp-horsefly syndrome |journal=European Annals of Allergy and Clinical Immunology| author1= Quercia, O.| author2=Emiliani, F. |author3=Foschi, F.G. |author4=Stefanini, G.F. |volume=40| issue=3| pages=61–63|pmid=18717054| url=http://www.researchgate.net/profile/Giuseppe_Stefanini/publication/23184186_The_wasp-horsefly_syndrome/links/02e7e5211bcb15460c000000.pdf}}</ref><ref>{{cite news| author=Williams, R. | url=https://www.independent.co.uk/news/uk/home-news/allergic-reaction-to-horsefly-bite-kills-father-of-four-in-seconds-after-anaphylactic-shock-8733207.html | title=Allergic reaction to horsefly bite kills father of four in seconds after anaphylactic shock | newspaper=The Independent | date=26 July 2013 | accessdate=9 September 2015}}</ref>

===Management===
Controlling horse-flies is difficult. [[Malaise trap]]s 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]].<ref>{{cite journal |title= l-Octen-3-ol, an effective attractant for Tabanidae (Diptera) |author1=French, Frank E.|author2=Kline, Daniel L. |doi=10.1093/jmedent/26.5.459 |journal=Journal of Medical Entomology |volume=26| issue=5 |year=1989 | pages=459–461}}</ref> 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.<ref>{{cite journal |title=Rigid canopy trap for Tabanidae (Diptera) |journal=Journal of the Georgia Entomological Society |volume=10 |issue=1 |year=1975 |pages=64–67 |author1=Axtell, R.C. |author2=Edwards, T.D. |author3=Dukes, J.C. |url=http://repository.lib.ncsu.edu/publications/bitstream/1840.2/2173/1/}}</ref> Cattle can be treated with pour-on [[pyrethroid]]s which may repel the flies, and fitting them with insecticide-impregnated eartags or collars has had some success in killing the insects.<ref name=IFAS/>

==Horse-fly bites==
Humans find horse-fly bites painful. Usually, a weal (raised area of skin) occurs around the site, and other symptoms may include [[urticaria]] (a rash), dizziness, weakness, wheezing, and [[angioedema]] (a temporary itchy, pink or red swelling occurring around the eyes or lips); a few people experience an allergic reaction.<ref>{{cite web |url=http://www.nhs.uk/Conditions/Bites-insect/Pages/Symptoms.aspx |title=Symptoms of insect bites and stings |date=27 June 2014 |publisher=NHS Choices |accessdate=30 September 2015}}</ref> The site of the bite should be washed and a cold compress applied. Scratching the wound should be avoided and an [[antihistamine]] 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.<ref>{{cite web |url=http://www.nhs.uk/Conditions/Bites-insect/Pages/Treatment.aspx |title=Treating insect bites and stings |date=27 June 2014 |publisher=NHS Choices |accessdate=30 September 2015}}</ref>

[[File:Theater of Insects.jpg|thumb|upright|[[Thomas Muffett]] described the horse-fly in his 1634 book ''Theatre of Insects''.]]

==In literature==

The [[Ancient Greek]] playwright [[Aeschylus]] has a gadfly pursue and torment [[Io (mythology)|Io]], a maiden associated with the moon, watched constantly by the eyes of the herdsman Argus, associated with all the stars: "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]], inspired by Aeschylus, has Tom o'Bedlam in ''[[King Lear]]'', "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.<ref name="Stagman2010">{{cite book |last=Stagman |first=Myron |title=Shakespeare's Greek Drama Secret |url=https://books.google.com/books?id=encnBwAAQBAJ&pg=PA207 |date=11 August 2010 |publisher=Cambridge Scholars Publishing |isbn=978-1-4438-2466-8 |pages=205–208}}</ref> In ''[[Antony and Cleopatra]]'', Shakespeare likens Cleopatra's hasty departure from the [[Battle of Actium|Actium battlefield]] to that of a cow chased by a gadfly: "The breeze [gadfly] 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 (mythology)|Juno]], who torments Io, and the cow in turn may allude to Io, who is changed into a cow in [[Ovid]]'s ''[[Metamorphoses]]''.<ref name="Walker2002">{{cite book |last=Walker |first=John Lewis |title=Shakespeare and the Classical Tradition: An Annotated Bibliography, 1961–1991 |url=https://books.google.com/books?id=q3Voi0Dk_HwC&pg=PA363 |year=2002 |publisher=Taylor & Francis |isbn=978-0-8240-6697-0 |page=363}}</ref>

The physician and naturalist [[Thomas Muffet]] 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 blowes through."<ref name="MarrenMabey2010"/> The "[[Jimmy Crack Corn|Blue Tail Fly]]" in the eponymous song was probably the mourning horsefly (''[[Tabanus atratus]]''), a tabanid with a blue-black abdomen common to the southeastern United States.<ref name=kaufman/>

==See also==
*[[List of soldierflies and allies of Great Britain]]
*[[Use of DNA in forensic entomology]]

==References==
{{reflist|30em}}

==External links==
{{Wiktionary|horsefly}}
{{commonscat-inline|Tabanidae}}<br>
{{Wikispecies-inline|Tabanidae}}

{{Diptera|2}}
{{Insects in culture}}

{{taxonbar}}
{{Authority control}}

{{DEFAULTSORT:Horse-Fly}}
[[Category:Tabanidae| ]]
[[Category:Biting insects]]
[[Category:Extant Late Jurassic first appearances]]
[[Category:Insects in culture]]
<!-- [[Category:Diptera families]] moved to Tabanidae redirect -->