Abstract
Records indicate that the present outbreak of the larch sawfly in Manitoba and Saskatchewan began about 1938 in the Spruce Woods-Riding Mountain area of Manitoba. Since then, it has spread in all directions where the principal host tree, larch, Larix laricina (Du Roi) K. Koch, occurs. It now includes nearly all of Manitoba and Saskatchewan, northwestern Ontario, part of northeastern Alberta, and northern Minnesota. In 1944, an annual survey of parasites that attack larvae of the larch sawfly was begun by the Forest Biology Laboratory, Winnipeg. The purposes of the survey were to determine (a) the principal species of parasites, (b) their abundance and effectiveness, and (c) .host-parasite population trends.
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