Abstract
The larch sawfly is a common defoliator of trees of the genus Larix throughout the Holarctic Region. In North America it has been reported from every province of Canada but in the United States it is confined to the northeastern States, the Lake States, and north-western Montana (Drooz, 1956). The northern limits of distribution have not been determined, but extend as far as 61° N. lat. north of Saskatchewan.