Beyond yellow: host plants of <i>Anthocharis euphenoides</i> in NW Italy

In recent decades, an alarming decline in butterfly populations has been documented in Europe. The main threats include changes in land use, pollution, and climate change. An in-depth understanding of the ecological requirements of species is crucial for developing effective conservation measures to counteract this decline. In this study, we aimed to clarify which plant species serve as host plants for Anthocharis euphenoides in the northernmost part of its Italian range. To gather valuable information for this purpose, we conducted an extensive survey of the butterfly, recording the plant species on which adult females were observed laying eggs or where pre-imaginal stages were present, as well as verifying the use of plants reported in the literature as potential host species. Our research revealed a predominant use of Erucastrum nasturtiifolium, with only a few cases in which Biscutella brevicaulis was used. The former host plant had been reported only in Spain and France, while the use of the latter was previously unknown. In no case was the reproduction of the butterfly associated with Biscutella laevigata, which is currently considered the main host plant in Europe, including Italy. The results highlight the need for a more thorough study of the ecological requirements of this butterfly, as misidentification of plants or the spread of unverified information from older literature may lead to inaccuracies in ecological knowledge, which is crucial for planning the conservation of oligophagous butterflies at a local scale.