Very few individuals have been captured to date. C. aestuans is found in the southern regions of all Canadian provinces, except Newfoundland. It also has an extensive distribution in the USA. The species is a major pest in western Canada, but is less abundant in eastern Canada, where it is found mainly near the Great Lakes and along the St. Lawrence River (Teskey, 1990).

Teskey (1960) is the only study in Ontario to mention captures of this species (six only) near Guelph. In Quebec, C. aestuans was common at Lac Boivin, Granby (Leprince & Lewis, 1982), but was only a minor component of the tabanid community at Trois Rivières (Baribeau & Maire, 1983). Lewis & Bennett (1977) collected few specimens in the Maritimes. Hanec & Bracken (1964) reported C. aestuans to be abundant in open farming areas of Manitoba (up to 55% of the tabanid catch), but rare elsewhere. Cameron (1926) also reported it to be an abundant species on the plains, extending into the northern forests. However, Thomas (1970) was able to find only three specimens in his review of Chrysops from Alberta. A paper by Pechuman quoted as in press by Teskey (1990) on the taxonomy of C. aestuans seems never to have been published.

Cobb & Balsbaugh (1976) and Easton (1982) reported that C. aestuans was abundant in South Dakota and was a common pest of man. This concurs with the description of Cameron (1926) of this species as "vicious in its blood sucking habits". It is therefore surprising that the literature on C. aestuans is as sparse as it appears to be.

Chrysops aestuans

Baribeau, L. & Maire, A. (1983) Abundance and seasonal distribution of Tabanidae in a temperate and in a subarctic locality of Québec. Mosquito News 43, 135-143.

Cameron, A.E. (1926) Bionomics of the Tabanidae (Diptera) of the Canadian Prairie. Bulletin of Entomological Research 17, 1-42.

Cobb, P.E. & Balsbaugh, E.U.,Jr. (1976) The Tabanidae (Diptera) of Spink County, South Dakota. Journal of the Kansas Entomological Society 49, 514-520.

Easton, E.R. (1982) Reduction of horse and deer flies on the Cottonwood Range and Livestock Experiment Station as a result of grazing. Journal of Economic Entomology 75, 292-294.

Hanec, W. & Bracken, G.K. (1964) Seasonal and geographical distribution of Tabanidae (Diptera) in Manitoba, based on females captured in traps. Canadian Entomologist 96, 1362-1369.

Iranpour, M. & Galloway, T.D. (2002) Chrysops, Hybomitra and Tabanus spp., horse and deer flies (Diptera Tabanidae). pp. 84-86 in Mason, P.G. & Huber, J.T. (Ed) Biological control programmes in Canada 1981-2000. Wallingford, Oxon, CABI International.

Iranpour, M. & Galloway, T.D. (2004) Three new Nearctic species of Telenomus (Hymenoptera: Scelionidae) attacking Tabanidae eggs. Canadian Entomologist 136, 43-60.

Iranpour, M., Schurko, A.M., Klassen, G.R. & Galloway, T.D. (2004) DNA fingerprinting of tabanids (Diptera: Tabanidae) and their respective egg masses using PCR - restriction fragment profiling. Canadian Entomologist 136, 605-619.

Leprince, D.J. & Lewis, D.J. (1982) Seasonal distribution of adult horse flies and deer flies (Diptera: Tabanidae) at lac Boivin, Granby, Quebec. Annals of the Entomological Society of Quebec 27, 94-99.

Lewis, D.J. & Bennett, G.F. (1977) Biting flies of the eastern maritime provinces of Canada. I. Tabanidae. Canadian Journal of Zoology 55, 1493-1503.

Pechuman, L.L. (1981) The horse flies and deer flies of New York (Diptera, Tabanidae), Second Edition. Search Agriculture 18, 1-66.

Teskey, H.J. (1960) Survey of insects affecting livestock in southwestern Ontario. Canadian Entomologist 92, 531-544.

Teskey, H.J. (1969) Larvae and pupae of some eastern North American Tabanidae. Memoirs of the Entomological Society of Canada 63, 147 pp.