Details are described of the breeding protocol, seasonal distribution of early stages, parasitism and pattern of emergence of Apatura iris (L.) in the neighbourhood of Basel, Switzerland from 1982 to 2002. Early stages are most readily found in the first three weeks of August. Eggs are laid between the leaf edges and the midrib. Males emerged significantly earlier than females. Emergence dates are related to spring temperatures; emergences have occurred earlier in the season year on year correlating with increasingly warmer springs. There was a gradual decrease in the numbers of imagines observed in the wild over the 21 years, possibly due to a decrease in the numbers of Salix caprea plants. Parasitism by Psilomastax pyramidalis Tischbein 1868 (Ichneumonidae), is discussed. Reproduction; Life cycle and development; Parasites diseases and disorders; Land zones; Palaearctic region; Eurasia; Europe Apatura iris (Nymphalidae); Reproduction; Life cycle; Parasites; Switzerland; Basel area; Biological observations none