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.
US Forest Service Alien Forest Pest Explorer, one can find maps of mountain ash sawfly distribution, and other pest information.
Mountain-ash sawfly damage.
Photo: Joselph O'Brien, USDA Forest Service, Bugwood.org
Mountain ash sawfly larvae.
Photo: Norman Buckley
Mountain ash sawfly.
Photo: Norman Buckley
Mountain ash sawfly larvae and damage.
Photo: Dave Pehling, WSU
Mountain ash sawfly.
Photo: Dave Pehling, WSU
Mountain ash sawfly.
Photo: Dave Pehling, WSU
Mountain-ash sawfly larvae.
Photo: Steven Katovich, USDA Forest Service, Bugwood.org