Found shortly before dusk, ensconced for the evening/night on the inner side of a large, incurved leaf of Veratrum californicum. The Veratrum was growing as a colony in a damp, low, patch of meadow shaded by fir and pines of the surrounding montane forest. Another male of the same species was found similarly perched about 40 feet away:

   

From gestalt of the color pattern & wing shape, this appeared to be a tiger moth...and a search though BugGuide images yielded a good match with Parasemia plantaginis, e.g. compare with the image below:

   

Powell & Opler(1)(2009) mention this is a polyphenic Holarctic species which, in North America, ranges from Alaska to Manitoba, and south through the Rocky Mountains to southern New Mexico...with isolated populations in the Sierra Nevada and the White Mountains of Arizona. They also mention adults are often found in the vicinity of lupine stands in moist relatively habitats, which was indeed the case here.

I take this to be a male, from the plumose antennae...the right one of which is tucked under its right wing.