Environmental impacts of genetically modified crops are mandatorily assessed during their premarket phase.One of the areas of conce is the possible impact on nontarget organisms.Crops expressing Cry toxins might affect Lepidoptera larvae living outside cultivated fields,through pollen deposition on wild plants,which constitute their food source.While pollen toxicity varies among different events,possible exposure ofnontarget species depends on the agro-environmental conditions.This study was conducted in two protected areas in Italy,characterized by different climatic conditions,where many Lepidoptera species thrive in proximity to maize cultivations.To estimate the possible exposure in absence of the actual stressor (e.g.,Cry 1-expressing maize plants),we conducted a two-year field survey of butterflies and weeds.Indicator species were selected Aglais (Inachis) io in the Northe site and Vanessa cardui in the Southe site—and their phenology was investigated.Pollen dispersal from maize fields was measured by collection in Petri dishes.Duration and frequency of exposure was defined by the overlap between pollen emission and presence of larvae on host plants.Different risk scenarios are expected in the two regions:highest exposure is foreseen forA.io in the Northe site,while minimal exposure is estimated for V.cardui in the Southe site.In the latter case,locally grown maize cultivars flower in mid-summer in coincidence with an aestivation period for several butterfly species due to hot and dry conditions.Moreover,host plants of V.cardui are at the end of their life cycle thus limiting food availability.