The thermal environment has a strong effect on the activity and behaviour of flying ectotherms, like butterflies. This project aims to understand the seasonal changes in behaviour, morphology and their interactions in multivoltine, temperate butterflies. Study species are – among others – the Speckled wood (Pararge aegeria), Green-veined white (Pieris napi) and the Map (Araschnia levana). Complex seasonal interactions between ‘design’ and behaviour (mate-locating and dispersal) are analysed. Spatial variation in seaonal interactions is also taken into account (differences in design-behaviour relationships among habitat types and differently fragmented woodland types). Comparative morphological analyses and behavioural studies between seasonal forms are done for the other species. Flight performance and thermoregulation are central issues. This project combines research on phenotypic plasticity with behavioural ecological and functional morphological research.