Spokane, Spokane County, Washington, USA August 8, 2014 Size: 12 mm
Size is a guestimate, due to the speed these guys were flying at. The flower is Anchusa officinalis - Common Alkanet. Many similar bees on a large plant but small and fast, so I picked the most representative. My guess is Anthidium manicatum, but so many similarly colored bees in the Megachilinae, I thought I'd leave it to the experts.