ISSN 1911-2173

Tabanidae of Canada, east of the Rocky Mountains 2: a photographic key to the genera and species of Tabaninae (Diptera: Tabanidae)

Anthony W. Thomas

Fredericton, New Brunswick,

June 06, 2018: An addendum has been published for this paper — doi: 10.3752/cjai.2018.AC01

Tabanidae of Canada, east of the Rocky Mountains 2: a photographic key to the genera and species of Tabaninae (Diptera: Tabanidae)

Tabanidae of Canada, east of the Rocky Mountains 2: a photographic key to the genera and species of Tabaninae (Diptera: Tabanidae)

Anthony W. Thomas

Fredericton, New Brunswick,

June 06, 2018: An addendum has been published for this paper — doi: 10.3752/cjai.2018.AC01


Interactive keys are provided for the 3 subfamilies of Tabanidae in Canada east of the Rocky Mountains. Keys are also provided for the 4 genera and 80 species (known and expected) of the subfamily Tabaninae in this region: 2 species of Haematopota Meigen, 40 species of Hybomitra Enderlain, 12 species of Atylotus Osten Sacken, 24 (plus two expected) species of Tabanus Linnaeus. Distribution maps for all species are provided, incorporating additional records since the most recently published maps (Teskey 1990).

Tabanus novaescotiae Photo by A. Thomas


The present contribution is an illustrated key to the Canadian Tabaninae east of the Rocky Mountains and is the final part for the eastern Canadian species of Tabanidae following the initial article (Thomas & Marshall 2009) on the subfamilies Chrysopsinae and Pangoniinae that also includes a general introduction and characterization of the family.

These keys are to females only as male Tabaninae are not commonly encountered, except that males of Atylotus spp. are collected as often as females; although neither sex, of Atylotus spp., is commonly collected. Also, I have not seen males of several of the Tabaninae species. Males are keyed in Teskey (1990).

Distribution maps herein are based on the maps in Teskey (1990), with the addition of post-1990 records from the University of Guelph Insect Collection (Department of Environmental Biology; DEBU), and from the author’s personal collection (AWT).

When this project (Tabanidae of Canada, east of the Rocky Mountains) was started, Teskey’s (1990) ``The Horse Flies and Deer Flies of Canada and Alaska`` was out of print and not readily available. However after CJAI published Part 1 and after much of the current MS had been written, The Entomological Society of Canada made Teskey (1990) available online:

The current work supplements Teskey (1990) with updated distribution maps and colour photos of all species east of the Rockies, including paratypes of Hybomitra agora Teskey, Hybomitra enigmatica Teskey, Atylotus calcar Teskey, Atylotus hyalicosta Teskey, Atylotus palus Teskey, Atylotus sphagnicolus Teskey, and Atylotus woodi PechumanThese photos will make for simpler and more accurate identification when used in conjunction with the current keys or Teskey’s (1990) keys.

For the beginner, good quality specimens, complete with antennae and palpi, are needed for identification. Because of the inevitable variation within species a series of specimens, from the same locality and capture date, are more useful than a single specimen for correct identification.
The following brief comments are not meant as a criticism of Teskey (1990) but simply to document differences between this current project and Teskey (1990) and also to correct some of the errors/inconsistencies in Teskey (1990).

I am rejecting Haematopota champlaini (Philip) as a Canadian species (see Haematopota page).

Teskey (1990) failed to comment on the strange distribution of Hybomitra frontalis (Walker) in Atlantic Canada.
Where found in Canada (transcontinental) it is usually abundant and a major pest. Thus its virtual absence from inland areas of Newfoundland & Labrador and the rest of Atlantic Canada is not readily accounted for. It is a common pestiferous species in the Atlantic salt-marshes of New Brunswick. The distribution of H. frontalis mirrors that of Chrysops furcatus Walker, a species with a continuous distribution from British Columbia to eastern Ontario, but absent further east until it becomes abundant on the same salt-marshes . McAlpine (1961) discounted the possibility that these Atlantic coast populations of Hybomitra (T. frontalis Walker, T. incisus Walker, T. septentrionalis Loew, T. labradorensis (Enderlain)) were anything other than morphs of the widely distributed inland species and suggested that they are all from a single interbreeding population. The large gap between the coastal population and the inland population negates any likelihood of interbreeding.

Hybomitra liorhina (Philip) can be exceedingly abundant on the Tantramar Marshes of extreme SE New Brunswick in early August as opposed to “apparently not very abundant at any locality, collections of only one or two specimens being the rule” (Teskey 1990, p. 213).

I am treating Hybomitra nuda (McDunnough) as a species and not as a subspecies of Hybomitra nitidifrons (Szilady); see Philip and Lane 1984.

The distribution of Hybomitra opaca (Coquillett) is uncertain. Teskey (1990) states (p. 225) “Canadian records for this species are only from Alberta” whereas his map on the same page shows a distribution dot in Saskatchewan. Burger (1995) lists it from Alberta and Saskatchewan.

A 5th Canadian specimen of Atylotus intermedius (Walker) is now known from Ontario, in the DEBU collection. Teskey reported only 4 other Canadian specimens of this incredibly rare species from Ontario.

Atylotus ohioensis (Hine) is confirmed as a Canadian species from specimens in the DEBU collection. Teskey predicted (p. 271) its occurrence in Ontario and Burger (1995) included southern Ontario in the distribution.

Teskey (p. 325) is inconsistent regarding the distribution of Tabanus novaescotiae Macquart in the Maritimes. On page 325 he states “Two collections have been made in the Maritime Provinces” whereas his map (p. 234) shows dots for 9 localities. Similarly for Tabanus catenatus Walker on page 308 he states “… with two collections in the Maritime Provinces” whereas his map (p. 307) shows dots for 4 localities.

Tabanus sackeni Williston is now known from 23 specimens in the DEBU collection with a range extension further north than extreme SW Ontario. Teskey listed only 2 Canadian specimens.

A specimen of Tabanus americanus Forster in the DEBU collection from eastern Ontario (Ottawa River) extends this species range in Canada from extreme SW Ontario.

Tabanus calens Linnaeus is now known from specimens in the DEBU collection from eastern Lake Superior; only in extreme SW Ontario in Teskey 1990.

Tabanus fairchildi Stone has been found to be widespread and relatively common is SW New Brunswick. Teskey recorded it from only 3 localities in Ontario and mentioned a single record from Quebec.

Tabanus limbatinevris Macquart is now known to occur further east than reported in Teskey, with 29 specimens in the DEBU collection vs. “known in Canada only from a few specimens … collected in Essex, Kent, and Lambton counties” (Teskey 1990, p. 316).

Under Remarks for Tabanus marginalis Fabricius (p. 319) Teskey states “Adults of  T. marginalis are not frequently collected”, whereas his map (p. 320) shows a large number of collection sites. In New Brunswick this species is widely distributed in the south and is frequently collected.

Tabanus nigripes Wiedemann is now known from as far west as north of eastern Lake Superior (DEBU collection). Previously only as far west as Georgian Bay.

A specimen of Tabanus subniger Coquillett in the DEBU collection from Oakville, Ont. (10 June 1978) adds to the single record in Teskey from 1932.

Tabanus sulcifrons Macquart is now known from a further 8 locations in SW Ontario other than those in the Niagara Peninsula reported in Teskey. Specimens in the DEBU collection from 12 locations.

In Teskey’s key that separates females of Tabanus sulcifrons from T. limbatinevris (p. 285) some of the text is reversed. In T. sulcifrons the cell is rarely closed (not closed and petiolate as stated) whereas in T. limbatinevris the cell is closed and often petiolate (not rarely closed as stated).

Tabanus trimaculatus Palisot de Beauvois is now known from a further 4 locations in SW Ontario (in the DEBU collection). Teskey reported 1 known Canadian specimen from Guelph, Ont.


Checklist/Index of Tabaninae species east of the Rocky Mountains

Haematopota Meigen

H. americana Osten Sacken
H. rara Johnson

Hybomitra Enderlein

H. aequetincta (Becker)
H. affinis (Kirby)
H. agora Teskey
H. arpadi (Szilady)
H. astuta (Osten Sacken)
H. aurilimba (Stone)
H. brennani (Stone)
H. captonis (Marten)
H. cincta (Fabricius)
H. criddlei (Brooks)
H. enigmatica Teskey
H. epistates (Osten Sacken)
H. frontalis (Walker)
H. frosti Pechuman
H. fulvilateralis (Macquart)
H. hearlei (Philip)
H. hinei (Johnson)
H. illota (Osten Sacken)
H. itasca (Philip)
H. lanifera (McDunnough)
H. lasiophthalma (Macquart)
H. liorhina (Philip)
H. longiglossa (Philip)
H. lurida (Fallen)
H. melanorhina (Bigot)
H. microcephala (Osten Sacken)
H. minuscula (Hine)
H. nuda (McDunnough)
H. opaca (Coquillett)
H. osburni (Hine)
H. pechumani Teskey & Thomas
H. pediontis (McAlpine)
H. rhombica (Osten Sacken)
H. rupestris (McDunnough)
H. sexfasciata (Hine)
H. sodalis (Williston)
H. tetrica (Marten)
H. trepida (McDunnough)
H. typhus (Whitney)
H. zonalis (Kirby)

Atylotus Osten Sacken

A. bicolor (Wiedemann)
A. calcar Teskey
A. duplex (Walker)
A. hyalicosta Teskey
A. insuetus (Osten Sacken)
A. intermedius (Walker)
A. ohioensis (Hine)
A. palus Teskey
A. sphagnicolus Teskey
A. sublunaticornis (Zetterstedt)
A. thoracicus (Hine)
A. woodi Pechuman

Tabanus Linnaeus

T. americanus Forster
T. atratus Fabricius
T. calens Linnaeus
T. catenatus Walker
T. fairchildi Stone
T. fratellus Williston
T. fulvicallus Philip
T. limbatinevris Macquart
T. lineola Fabricius
T. marginalis Fabricius
T. nigripes Wiedemann
T. nigrovittatus Macquart
T. novaescotiae Macquart
T. pumilus Macquart
T. quinquevittatus Wiedemann
T. reinwardtii Wiedemann
T. sackeni Fairchild
T. sagax Osten Sacken
T. similis Macquart
T. sparus Whitney
T. stygius Say
T. subniger Coquillett
T. sulcifrons Macquart
T. superjumentarius Whitney
T. trimaculatus Palisot de Beauvois
T. vivax Osten Sacken

Subfamily Key


Genus Haematopota Meigen

Small, slender, tabanids (length 7-11 mm) with head distinctly wider than high and a wing pattern of intricate grey or brown pigmentation.

Burger (1995) listed 5 species from North America including 3 species from Canada: americana Osten Sacken, rara Johnson, champlaini (Philip). The first two undoubtedly occur in Canada. The record for champlaini is based on 1 specimen, in the G.B. Fairchild collection, from Black Sturgeon Lake (BSL) Ontario (near and north of the northern border of Lake Superior). Teskey (1990) included champlaini as part of the Canadian fauna without further comment other than “This species has been rarely collected.” and “The only other collections are from Rhode Island and west-central Pennsylvania.” Burger & Pechuman (1986) commented on the BSL specimen and noted differences between it and the type material. It seems unlikely that the range of chamlpaini  would include the boreal forest of Canada and so this species is not included in the key. 

A key, descriptions, and distribution maps for all 5 North American species can be found in Burger & Pechuman (1986). 


Genus Hybomitra Enderlain

These are the commonest Horse Flies in Canada being outnumbered further south by Tabanus spp. They range in length from 10-20 mm and have an eye pattern, in life, that usually involves 3 or 4 green transverse stripes on a dark background. All species are probably blood-feeders and are attracted to traps such as the Manitoba Fly Trap (see Pechuman 1981).

Four species (aequetincta, arpadi, lurida, sexfasciata) are Holarctic in distribution. A fifth species, H. nuda (McDunnough), is listed as a subspecies of the Palaearctic H. nitidifrons (Szilady) in Teskey (1990) and in Burger (1995). Philip and Lane (1984) questioned the validity of this placement and concluded there was insufficient evidence to reduce nuda to a subspecies of nitidifrons; I follow their opinion.

Characters that are commonly used in key couplets (subcallus, pruinose/denuded glossy; notopleural lobe, red/black; abdomen, warm-brown/grey-black) vary widely in minuscula, tetrica, frontalis and each of these species keys out in more than one couplet. Hybomitra frontalis is especially variable, (McAlpine (1961) described 8 colour morphs) and some of its many forms resemble pediontis and tetrica.

Flies belonging to one of the 22 species with a pruinose subcallus may be difficult to identify when excessively worn. In rare cases the subcallus may become bare and shiny, due to wear, which will lead to choosing the incorrect alternative in couplet 6.

Teskey (1990) listed 47 species of Hybomitra from Canada and Alaska; I treat the 40 species which occur east of the Rocky Mountains; 23 of these 40 species also occur in British Columbia.


Genus Atylotus Osten Sacken

Small to medium species, 8-15 mm in length, most similar to species of Tabanus. Head features are characteristic and include hairy eyes with either a single darker stripe or no stripe. Female frons either completely pruinose with no calli or with a small median and a small basal callus well separated from the eyes. 

Of the 14 North American species, 13 are found in Canada with12 found east of the Rocky Mountains. Atylotus adults rarely, if ever, stray far from the larval habitat. Females of some species are known to be blood-feeders whereas females of other species are suspected of being non-blood feeders.

Atylotus intermedius varies in the presence/absence of frontal calli and thus keys out in two couplets. The 4 species with frontal calli (includes intermedius) are relatively easy to separate. The 9 species that lack frontal calli (includes intermedius ) are very similar and it is not always possible to identify an individual. These species lacking frontal calli have similar facies and identification is heavily dependent upon colour of hairs and thus worn specimens, i.e., lacking hairs, are difficult or impossible to identify to species. 

Teskey (1990) included A. ohioensis in his key with the expectation that this species occurs in southern Ontario; Burger (1995) listed it from Ontario. I include this species in the following key as there are specimens in the DEBU collection that were collected in southern Ontario.

Teskey (1983, 1990) are the most useful publications for descriptions of the eastern species.


Genus Tabanus Linnaeus

Large to small species, 8-27 mm in length, most similar to species of Hybomitra. Head features are characteristic and include the head vertex lacking an ocellar tubercle and eyes lacking hairs. A plain unmarked eye, no stripe or band, in some species (only for live flies) is a useful generic character; eye always striped or banded in Hybomitra spp.

Unlike in Hybomitra, a denuded subcallus is rare in eastern Canadian Tabanus spp. It is only consistently denuded in atratus and partially denuded in nigripes. In pumilus the normally pruinose subcallus frequently shows small to large denuded patches (due to wear?). For this reason I have included this species in two couplets.

Of the 30 species found in Canada 24 are found east of the Rocky Mountains. Most Tabanus species, 22, are found in Ontario with only 11 species occurring east of Ontario and 7 species west of Ontario and east of the Rockies. Teskey (1990) suggested that a further 2 species (sparus, superjumentarius) possibly occur in Ontario. Although still not recorded from Canada these two species are included in the key and images are shown and short descriptions given.

Two species, calens, pumilus, are sufficiently varied for each to key out in more than one couplet.

For a full diagnosis of the genus and detailed description of species, and for all genera and Canadian species in the Tabanidae see Teskey (1990).

There are a few errors and omissions in Teskey (1990). Perhaps the most significant is in the key on page 285 to separate the females of sulcifrons and limbatinevris; it should read:

  1. Cell r5 narrowed to apical margin but rarely closed. Frons . . . . . . . . . . . . . . . . . . . . . . . . sulcifrons

-      Cell r5 usually closed at cell margin or petiolate. Frons . . . .  . . . . . . . . . . . . . . . . . . . . . . limbatinevris

The text in the description of these 2 species, p.315 & p.344, is correct


This study would not have been possible without the assistance of the staff at the Canadian National Collection. I specifically wish to thank Dr. D.M. Wood who selected 41 specimens of several of the rarest tabanids for me to photograph and facilitated their loan; also thanks to Dr. Bradley Sinclair for authorizing the loan and sending me the specimens. I thank Alan Fleming (CNC) for the excellent image of Tabanus subniger.

Many of the new distribution records are based on the University of Guelph Insect Collection database funded by the CFI CANADENSYS grant and I thank Dr. Marshall for allowing me access to this database and Steve Paiero for distribution maps of the species in that collection. I thank David Cheung (UofG) for supplying the base maps of Canada and for his organization of the gallery images.

Although not directly associated with this study I wish to acknowledge the mentorship of the late Drs. G.B. Fairchild, L.L. Pechuman, and H.J. Teskey.

I thank Drs. Bruce Ezell and Mac Tidwell who facilitated my collecting of specimens in South Carolina and supplied me with tabanids from Louisiana. Such specimens helped enormously in my appreciation of species recognition.

I thank Dr. S.A. Marshall for the use of his images of live tabanids in the keys and in the Gallery. For the face shot of a live Tabanus americanus I thank Sturgis McKeever (image citation: Sturgis McKeever, Georgia Southern University,, image used under a Creative Commons Attribution-Noncommercial 3.0 United States License:

I thank Dr. Steve Marshall and his staff at Guelph for their continual encouragement and support for this study.

This article has benefited from comments by Dr. Marshall and two anonymous reviewers, my thanks to them.


Burger, J.F. 1995. Catalog of Tabanidae (Diptera) of North America north of Mexico. Contributions on Entomology, International. Vol. 1, No. 1. Associated Publishers, Gainesville, Florida, USA. 100pp.

Burger, J.F. and L.L Pechuman. 1986. A review of the genus Haematopota (Diptera: Tabanidae) in North America. J. med. Ent. 23(4):345-352.

McAlpine, J.F. 1961. Variation, distribution and evolution of the Tabanus (Hybomitra) frontalis complex of horse flies (Diptera: Tabanidae). Can. Ent. 93: 894-924.

Osten Sacken, C.R. 1876. Prodrome of a monograph of the Tabanidae of the United States. Part II. The genus Tabanus. Mem. Boston Soc. Nat. Hist. 2: 421-479.

Pechuman, L.L. 1964. A list of the Tabanidae (Diptera) of Quebec. Can. Ent. 96(12): 1495-1496

Pechuman, L.L. 1981. The Horse Flies and Deer Flies of New York (Diptera, Tabanidae), 2nd edition. Search Agric. 18. 68pp.

Pechuman. L. L., D.W. Webb and H.J. Teskey. 1983. The Diptera, or True Flies, of Illinois. I. Tabanidae. Bull. Illinois Nat. Hist. Survey.  33(1): 4 + 122 pp.

Philip, C.B., and R.S. Lane. 1984. Comments on the presumed Holarctic occurrence of the horse fly Hybomitra nitidifrons (Diptera: Tabanidae). International J. Ent. 26(3): 286-288.

Stone, A. 1938. The horse flies of the subfamily Tabaninae in the Nearctic region. USDA Misc. Publ. 305. 171 pp.

Teskey, H.J. 1983. A revision of eastern North American species of Atylotus (Diptera: Tabanidae) with keys to adult and immature stages. Proc. ent. Soc. Ont. 114: 21-43.

Teskey, H.J. 1990. The Insects and Arachnids of Canada. Part 16. The Horse Flies and Deer Flies of Canada and Alaska. Diptera: Tabanidae. Publication 1838. Research Branch, Agriculture Canada, Ottawa. 381pp. Available online at:

Thomas, A.W. and Marshall S.A. 2009. Tabanidae of Canada east of the Rocky Mountains 1: a photographic key to the species of Chrysopsinae and Pangoniinae (Diptera: Tabanidae). Canadian Journal of Arthropod Identification No. 8, 25 June 2009, available online at:, doi: 10.3753/cjai.2009.08

Cite this article

Thomas, A. Tabanidae of Canada, east of the Rocky Mountains 2: a photographic key to the genera and species of Tabaninae (Diptera: Tabanidae) Canadian Journal of Arthropod Identification No.13, 16 February 2011, available online at doi: 10.3752/cjai.2011.13

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