It has been established that a complex of predacious arthropods on apple trees in Nova Scotia can control phytophagous mite populations (Lord, 1949). Some of the predators, when sufficiently numerous, may also be important in the control of other pests such as the eye-spotted bud-moth, Spilonota ocellana (D. & S.), and the codling moth, Carpocapsa pomonella (L.). When predation has reduced the mite population to small numbers, the insect predators almost disappear from the orchard. In most orchards in this province, the use of spray materials innocuous to predators has greatly reduced the phytophagous mite populations. The low mite population is an important gain but it is not known whether the attendant small numbers of predators is advantageous in the natural control of pests in general. This will be answered in time by the experience of the growers and, meanwhile, further research is needed on the interrelations of the phytophagous and predacious species and on how they are affected by orchard practices and other factors. This involves studies on the food preferences and behaviour of many species. In addition, means must be found to modify cultural practices to make conditions as favourable as possible for certain species of predators.