The western hemlock sawfly, Neodiprion tsugae Middleron, first came to our notice from the Queen Charlotte Islands, British Columbia. In 1931, reports of the dying of hemlocks over large areas came from rangers and timber operators of this region. A survey conducted by Mr. W. G. Mathers of the Dominion Entomological Branch, in September and October of that year, indicated that the injury extended over approximately forty square miles. In 1932, the outbreak showed definite signs of subsiding, and had practically disappeared by 1933, although many trees were killed during the peak year of 1931, indicating that this is a primary enemy of western hemlock, and that outbreaks may be expected from time to time in the Pacific Northwest.