Abstract
Wild bees and hoverflies are key pollinators, but their populations are declining in Europe. As the monitoring of each species would be arduous to implement, a cost-effective solution could be a shift from species level monitoring to an evaluation of the trends of functional groups. However, the lack of centralized trait databases hampers progress, as data are often dispersed across literature, limited to some countries or remain as expert knowledge. In a comprehensive effort of scientists working on these two insect groups, data on traits of 3,052 European bee and hoverfly species (2139 and 913, respectively) was compiled. The dataset includes 18 shared traits, along with additional group-specific traits-13 for wild bees and eight for hoverflies. These traits span nesting ecology, larval biology, adult morphology, behavior, and distribution patterns. The primary data sources consist of literature reviews, experimental studies, and expert insights. By fostering collaboration among researchers, this dataset provides a new foundation for exploring the ecological roles of these vital insect pollinators, guiding targeted conservation strategies, and deepening our understanding of the mechanisms of pollinator decline in Europe.