AbstractGynaephora groenlandica(Wocke) (Lepidoptera: Erebidae) is a cold-adapted species, whose life history traits are dictated by cold and short Arctic summers. We used a recently discovered alpine tundra population in southwestern Yukon, Canada to investigate local adaptations to habitats with different environmental conditions (alpine versus Arctic). Using cafeteria-type experiments and field observations we examined the diet breadth of alpine populations ofG. groenlandica beringianaSchmidt and Cannings, and compared these to published data on High Arctic populations ofG. groenlandica groenlandicaand to the closely relatedG. rossiiCurtis.Gynaephora groenlandica beringianaappears to have a broader diet than High Arctic populations, but similar to that exhibited by alpine populations ofG. rossii. Such trends could emerge from reduced synchrony between herbivores and their host plants in less extreme environments, and possibly from a reduced incidence of parasitoids in the life cycle of these populations. Our findings indicate the larval host plant plasticity ofG. groenlandicain different environments, and are relevant to predictions regarding the fate of these populations under climate warming scenarios.