The Biological Control Factors of the Immature Stages of Euxoa Ochrogaster Gn. (Lepidoptera, Phalaenidae) in Saskatchewan.*

In approaching an economic problem from the ecological viewpoint, as is so often necessary in investigations of insect pests, a study of the part played by natural control factors is generally of great practical importance as well as of scientific interest. A knowledge of the factors involved and their mode of operation explains the fluctuations in numbers of the pest and should eventually provide a means of anticipating developments. These considerations give a dual bearing to the study of the more important biotic factors affecting the principal cutworm of Saskatchewan, the red-backed cutworm (Euxoa ochrogaster Gn.). The data presented in this preliminary report have been accumulated during the four years 1923 to 1926 and, while the details relate in the main to conditions at Saskatoon, the principles brought out apply throughout the province of Saskatchewan.