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Abstract. 1. Agricultural intensification is considered to be a major driver of terrestrial biodiversity decline. Resulting loss, isolation and degradation of flower-rich habitats are threatening pollinators. Agri-environmental schemes (AES) aim to counteract these negative effects, including measures to enhance floral resources in agricultural landscapes. The impact of plant species composition on their efficiency to mitigate pollinator loss, however, is largely unexplored.2. We tested four recommended seed mixtures for their attractiveness to wild bees and hoverflies in a replicated plot design over two consecutive years against the background of the seedbank. Of the 94 available plant species, 14 key plant species were crucial for the whole flower-visiting bee and hoverfly community. Approximately one third of each originated from the seedbank. The four top plants already supported 80% of flower visitors. Although seed mixtures differed significantly in attracting flower visitors at the plot level, the presence of key plants was more important than plant species diversity per se.3. Seed mixtures showed contrasting attractiveness for wild bees and hoverflies. Identification of plant species exclusively utilised by specific taxonomic groups opens opportunities for assorting plant mixtures for specific ecosystem functions or taxa of conservation concern. Plant species shared by common pollinators are valuable for overall pollinator diversity.4. The fact that rare and specialised pollinator species were mostly absent, however, substantiates that within 2 years of establishment, flowering resources are not the sole limiting factor in modern agricultural landscapes. Considering additional resources seems indispensable to maximise the conservation of species-rich pollinator communities.

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Abstract. 1. Sown wildflower strips can support insects that collect pollen for their larvae. How these strips affect flower visitors with carnivorous larvae, however, is almost unknown. We studied the impact of wildflower strips and their surroundings on two common solitary wasps: the caterpillar-hunting Ancistrocerus nigricornis Curtis and the spider-hunting Trypoxylon figulus Linnaeus.2. Trap-nest locations at 22 semi-natural habitats in central Germany formed independent gradients in landscape complexity and distance to either one or several wildflower strips in their surroundings. For each brood cell, we recorded the number of prey items, total caterpillar weight and spider species richness.3. Ancistrocerus nigricornis built more cells in proximity to wildflower strips and with increasing amount of surrounding grassland. Fewer prey items provided in landscapes with large shares of semi-natural habitats suggest that in these landscapes high-quality prey is available. In contrast, T. figulus built more cells with increasing distance of nests to wildflower strips. If there were few strips, T. figulus built more cells in grassland-rich landscapes, whereas low shares of grassland were compensated when several wildflower strips were present. Benefits of flowering strips for T. figulus seem related to flower resources for adults, rather than through prey provisioning.4. In conclusion, wildflower strips promote prey-hunting wasps through species-specific effects on adult and larval food provisioning. Considering the differential effects of wasps on crop pests (caterpillars) and natural enemies (spiders), the functional role of wildflower strips in agroecosystems may be much greater than assumed when solely focusing on pollination.