Abundant in the Sierra Nevada from about 4000' to tree-line; occasionally lower in canyons with cold-air drainage (as at Washington). There is a "no-man's land" in the foothills occupied by neither P. campestris campestris nor P. c. montana. In northwestern and northeastern California, north of the range of P. c. montana, P. c. campestris goes right up to tree-line! The northern end of the range of the Sierran-endemic entity montana is occupied by a swarm of intermediate and highly variable populations throughout the Feather River drainage. At Beckwourth Pass, NNE of Sierraville in shrub-steppe high desert, the mix includes Great Basin phenotypes variously styled vallis and camillus. The Sierra Valley population of intergrades is extinct and has seemingly been replaced by montana at low density.
The Montana Crescent is found in meadows, woods edges, trailsides and successional sites, wherever its hosts, Aster species, grow. It swarms over puddles and Aster (and many other) blossoms. The one brood extends from June through August. At Lang and very rarely at Donner there is a partial second emergence in September.