Mountain ash sawfly, Pristiphora geniculata (Hartig), was just confirmed present in the summer of 2009 in Snohomish County, Washington State. It is a new western North American record for this insect. Useful links:
Forest Pests: Mountain ash sawfly
Cornell Insect diagnostic lab: mountain sawfly
Maine Department of Conservation. 2000. Mountain ash sawfly. Maine Forest Service - Forest Health and Monitoring Division. 19 March 2012.