Parnassius smintheus, the Rocky Mountain parnassian or Rocky Mountain apollo, is a high-altitude butterfly found in the Rocky Mountains throughout the United States and Canada. It is a member of the snow Apollo genus (Parnassius) of the swallowtail family (Papilionidae). The butterfly ranges in color from white to pale yellow-brown, with red and black markings that indicate to predators it is unpalatable. Parnassius smintheus primarily feeds on the leaves of the Sedum lanceolatum plant as larvae and on its nectar as adults. The butterfly tends to reside in meadows and avoids forests, because it strongly prefers light. The males of this species fly from meadow to meadow frequently to find females and food resources, whereas females are more likely to avoid flying. The males seem to have mate choice in this species, as they emerge from the pupae earlier than the females and patrol for females, heavily preferring newly emerged females that have not yet flown. Although the species is not yet endangered, the climate change and human activity over the last few decades have reduced its viable habitats, and this process is continuing. Range and habitat The range of the butterfly is based primarily in the Rocky Mountains, which spans Canada and the United States. This includes the mountainous areas of Yukon, Alaska, and British Columbia in Canada, and as far south as New Mexico in the United States. P. smintheus can often be found in alpine and subalpine meadows. It was found that males of this species preferred meadows with a greater abundance of nectar flowers and a higher quantity of the host plant Sedum lanceolatum. They also preferred meadows with a greater number of females of their species. Males may sample two or more meadows to gain information on their relative quality. It has been suggested that this preference in males for meadows with more food resources may be due to their increased energy requirements, as they spend much more time flying than females. In contrast, the female butterflies showed no preference for meadows with more nectar flowers or host plants, or for greater numbers of males. Food resources The primary larval host plant is Sedum lanceolatum, spearleaf stonecrop, a yellow-flowered perennial succulent common in rocky habitats in Western North America. Larval foodplants may less frequently include other stonecrop species, including S. divergens, S. oreganum, S. stenopetalum, and S. integrifolium. The foodplants tend to grow most abundantly