We believe this is a plume moth caterpillar, a distinctive group of moths that look like a capital “T” or like a glider at rest. Caterpillars are hairy or bristly, various colors, and feed on plants, with some species rolling leaves to feed inside and others boring into stems. There are over 160 species of plume moths in the US and Canada, primarily found in the west …making identification to exact species very difficult.
Photo by: Heather McKee on 5/28/21 in Missoula, MT