Psilomastax pyramidalis, an ichneumonid parasitoid of Apatura iris, is recorded for the first time from Switzerland (BL, Allschwil) and France (Haut-Rhin, Hagenthal). In 1993 and 1998-2002 the parasitoid appeared in rearings of A. iris in numbers which are unusual. The parasitoid is generally considered to be very rare. In these years the degree of parasitism ranged from 10 % to slightly over 20 %. In the period of 19821992 P. pyramidalis was never observed. The reason for these unexpected findings may be the usually ill-matched phenologies of the host and parasitoids, and the improved match with the changing phenology of A. iris over the last ten years. It is suggested here that the susceptible stages of A. iris may be the first and/or second instar caterpillars and maybe the egg. Apatura iris (Nymphalidae) : Host Psilomastax pyramidalis (Ichneumonidae) : Parasite New record Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts; Ecology; Population dynamics; Land zones; Palaearctic region; Eurasia; Europe Apatura iris; Hymenopteran parasites; Parasite irruption; consequence of host parasite phenology matching; France & Switzerland; Psilomastax pyramidalis; France; Haut-Rhin, Hagenthal; Switzerland; Baselland, Allschwil Psilomastax pyramidalis; Lepidopteran hosts; Irruption as parasite; consequence of host parasite phenology matching; France & Switzerland; Apatura iris; Irruption; France; New record; lepidopteran host; Haut-Rhin, Hagenthal; Switzerland; Baselland, Allschwil none