DISTRIBUTION OF THE FACE FLY, MUSCA AUTUMNALIS (DIPTERA: MUSCIDAE), IN WESTERN CANADA AND THE RELATION BETWEEN ITS ENVIRONMENT AND POPULATION DENSITY

Abstract

The range of the face fly, Musca autumnalis De Geer, has extended from the site of its first North American occurrence in Nova Scotia in 1952 to the northern half of the United States from coast to coast and every province in Canada. The first recorded appearance in Western Canada was at Virden, Man., in 1964 and it has since become established in eastern Saskatchewan. Face flies moved from Washington and Idaho into British Columbia in 1966. In 1967 they spread to most areas of the southern half of British Columbia and into southwestern Alberta through the Crowsnest Pass. Moisture and shade in pastures influenced the numbers of face flies seen on cattle and resulted in higher numbers than under dry prairie conditions.