Abstract
During a study of the effects of spray chemicals on the arthropod communities of peach orchards in the Niagara Peninsula, Ontario, begun in 1946, Stethorus punctillum Weise was found to be one of the more important predators of tetranychid mites. An investigation of its biology was undertaken in 1949 and continued through 1952. This paper presents chiefly the life-history, behaviour, and ecological aspects.