none Euphydryas maturna; FOOD-PLANTS; Fraxinus excelsior & Viburnum opulus; FOOD-AVAILABILITY; Interspecific competition effects; DEVELOPMENT-; Phenology; HYMENOPTERAN-PARASITES; Cotesia bignelii; New host record; MORTALITY-; Herbivorous species impact; INTERSPECIFIC-COMPETITION; Herbivores impact on mortality & food availability; HABITAT-PREFERENCE; FOREST-AND-WOODLAND; Habitat preferences; CLIMATE-AND-WEATHER; Status relationships; SWEDEN-; Distribution, status & biology Cotesia bignelii; LEPIDOPTERAN-HOSTS; Euphydryas maturna; New host record; SWEDEN-; New lepidopteran host record. The Swedish occurrence of Euphydryas maturna (L.) is rapidly decreasing. The species is still rather frequent in a restricted area in the Central Swedish Vastmaland province. Preferred habitats were found along small streams on clearings in coniferous forest with a mixture of Populus, Salix, Betula, Sorbux, and the two foodplants Fraxinus excelsior and Viburnum opulus. Larval feeding were only observed on these two species. E. maturna preferred soils of a moderate fertility with a corresponding lower and sparser undergrowth of herbs among mosses and lichens, e.g., Vaccinium, Carex, Succisa, Melampyrum, and Pyrola. The development of E. maturna takes two or three years in Sweden. The larvae were parasitized by the gregarious endoparasite Cotesia bignelli (Marshall) (Ichneumonidae), not previously recorded from Sweden. It is suggested that low air temperatures in combination with much sunshine in spring may reduce the frequncy of parasitized mature larvae of E. maturna. Consequently, such weather conditions could be essential for the long time survival of the species. The studied inland localities are restricted to elevations between 150-250 m a.s.l. in moderate rainshadow with relatively much snow that lasts until April or May during cold winters. Snow is suggested to protect larvae from becoming active too early in spring when air temperatures may be high but sunshine is sparse. The impact of other herbivores on the host plants of E. maturna is discussed. The chrysomelid beetle Pyrrhalta viburni (Payk.) has periodical outbreaks on Viburnum. Moose feeds on fresh leaves of both Fraxinus and Viburnum, causing some mortality of E. maturna eggs, but avoids the larval nests.