The Apollo (Parnassius apollo) occurs in mountainous areas on steep, sunny slopes with sparse vegetation. In North America, there are many different subspecies, forms and aberrations, because of the fragmented distribution and consequently, isolation of populations. However, their ecology is similar. The butterflies are found visiting thistles and other flowering plants. The female lays its eggs singly or in small groups on or near the foodplant Stonecrop (Sedum spp.). The eggs develop but the tiny caterpillar hibernates inside the eggshell or as newly hatched larva in its close vicinity. In spring it starts feeding on the buds of the foodplant. The caterpillars of later instars also eat the leaves. When it is time to pupate, the caterpillars look for a safe place between the stones, where they then spin a flimsy cocoon in which to change into a pupa. The Apollo has one generation a year. Habitats: alpine and subalpine grasslands (23%), dry calcareous grasslands and steppes (19%), inland cliffs and exposed rocks (11%), screes (9%), coniferous woodland (7%), broad-leaved deciduous forests (7%).