During a stay at the Research Station, Canada Department of Agriculture at Kentville, Nova Scotia, from July 3 to October 16, 1959, I had the opportunity to make some observations on the natural enemies of the woolly apple aphid, Eriosoma lanigerum (Hausm.), the rosy apple aphid, Dysaphis plantaginea (Pass.), and the green apple aplud, Aphis pomi Deg. An inventory of these enemies was made in the Annapolis Valley in apple orchards. sprayed according to the principles of the spray schedule of Dr. A. D. Pickett. This schedule avoids spraying with fungicides and insecticides such as sulphur and phosphorus compounds, which are very harmful to the enemies of a number of pests, studied by Dr. Picktett and his staff (cf. Pickett 1959). The dipterous predators and their enemies are dealt with in this paper.