Dispersal and population dynamics of Stomoxys calcitrans (Diptera: Muscidae) in south-central Ontario

Stable flies (Stomoxys calcitrans) are noxious and economically significant pests of livestock and humans. They have a distribution from the tropics to the temperate zones where their occurrence is ultimately limited to the summer months by low winter temperatures. Using data from field sampling studies, the application of stable fly age-grading methods and a method of measuring stable fly physiological and behavioral processes on the basis of degree-days, this thesis develops models of stable fly population growth and dispersal on farms in south-central Ontario.;Life-history parameters for development time, adult survival, and fecundity, determined from five years of trap catch data obtained at a beef farm in the region, were assessed in terms of degree-days. I used these to construct a Leslie matrix model of stable fly population growth at the local population level with a degree-day based time step. This model was used to predict the outcome of various control strategies. Reducing the intrinsic rate of increase (r) by a low daily kill rate of adult stable flies over a sustained period proved most effective. Field tests supported the model's prediction that two permethrin killing stations at each of three farms would be able to significantly lower r, thus delaying the onset of pest population levels, compared to dairy farms without killing stations.;The region's stable fly population is re-established each spring by flies dispersing from local refuge farms rather than by long-distance, weather-borne migrants as some literature suggests. Refuge farms are more prevalent in the moderated climate near Lake Ontario, and decrease in density with distance from the lakeshore. It is argued that south-central Ontario stable fly populations exist as a metapopulation at the edge of the species' climatic range. Dispersal was modelled as an outward invasion from overwintering refuge populations on dairy farms using a gamma distribution and linked to refuge farm density. Dispersal appears to be density independent with a possible seasonal decrease in dispersiveness due to the presence of phoretic macrochelid mites.