These large hawkmoths (sphinx moths) are a non-native species that’s been released in the fight against leafy spurge (the food source for their beautiful caterpillars). They can be found in several western states (Montana, Idaho, and Oregon) as well as eastward to at least Michigan. Their range continues to grow. There can be one to two generations a year.
Photo by Taylor Marston on 8/17/20 in Missoula, MT.