Autecology of the Adult Horn Fly, Haematobia Irritans (L.), (Diptera: Muscidae)

Abstract

During the horn fly seasons of 1959 and 1960, experiments were conducted to determine the relationship of weather conditions to horn fly populations on three breeds of dairy heifers, to correlate the effect of the macroenvironment on the microenvironment within the 1/2 in. mantle of a heifer, and also to correlate the locations of horn flies within this mantle with various factors of the microenvironment. Usually there was a significant difference between the number of horn flies on Holstein and that on Guernsey and Jersey heifers. The flies generally preferred the dark—colored areas of biocolored cattle during daylight hours, and the black of the Holstein to the tan of the Guernsey. When the macrotemperature was above 85°C, many of the flies were found on the white skin of the belly and udder area of heifers. During inclement weather the flies were observed on both the white and dark—colored areas of all heifers. Macrotemperature and relative humidity influenced the horn fly populations within the biocenose. The apparently preferred macroclimate for macroclimate for horn flies was: temperature 73 to 80°F, relative humidity 65 to 90%, scattered light showers, and no wind. The flies apparently sought certain microenvironmental conditions most commonly observed on Holsetin heifers. Within the mantle of microenvironment, horn flies appeared to prefer an air temperature of about 85°F, a skin temperature of about 97°F, and a relative humidity of about 65%. When such conditions were not available to the flies on the sides and backs of Holstein heifers, the flies were usually found in near—optimum conditions along the belly midline for each of the three breeds of heifers.