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Flower strips are a prominent agri‐environmental scheme with the central objective to promote biodiversity and maintain associated ecosystem services. The promotion of natural enemies by increasing resource availability through flower strips is a promising approach for integrated pest management.In a 3‐year field study, two annual and two perennial flower strip mixtures, as well as a grass mixture, were tested regarding their attractiveness for natural enemies at three different study sites in Germany. Natural enemies were sampled annually in nine sampling rounds at a 10‐day rhythm using sweep netting and pitfall traps. To assess available floral resources, we estimated the species‐specific flower cover and classified species into flower types.Flower strip mixtures differed in their attractiveness to natural enemies. Treatment effects on arthropod activity density were most pronounced in the second and third year. Overall, perennial were more attractive than annual flower strip mixtures for most natural enemies, however, the response to flower strip mixtures varied significantly among taxa. For example, perennial flower strips showed a two‐ to fourfold increase of plant‐dwelling spider and parasitoid wasp activity density as well as higher numbers of juvenile stages of predatory bugs and rove beetles compared to annual flower strips. In contrast, annual flower strip mixtures showed the highest attractiveness for ground beetles. Moreover, different natural enemy taxa were associated with varying flower strip characteristics such as flower type proportion, herbivore availability and plant species richness.Synthesis and applications. We found taxon‐specific responses of natural enemies to different flower strips, which provide guidance for the floral composition of flower strips in order to maximize their effectiveness for natural pest control. We suggest the use of perennial mixtures with high proportion of flower heads (Asteraceae) and disk flowers (esp. Apiaceae, Rubiaceae, Brassicaceae) in particular, but also flag blossoms (Fabaceae) as these flower types were positively associated with several natural enemy groups. However, since we found mixed responses to flower types, specific flower strip composition will ultimately depends on its objective. [ABSTRACT FROM AUTHOR]

Abstract: Semi‐natural habitats (SNH) provide essential resources for many organisms in agricultural landscapes and can increase biodiversity at the local and landscape scale. For the management of ecosystem services, it is crucial to understand how local characteristics of SNH and the surrounding landscape complexity affect beneficial species. We investigated this for hoverflies (Diptera: Syrphidae)—an important functional group providing both pest control and pollination services—in a total of 138 SNH within 35 agricultural landscapes in Switzerland and Germany. SNH differed in type (woody, herbaceous), shape (areal, linear) and availability of food resources (floral resources and aphids). They were located along a gradient of landscape complexity (1%–75% SNH in a 1 km radius). In total, 9,030 hoverflies belonging to 89 species were collected. In both countries, hoverfly community composition was mainly driven by SNH type and SNH shape, in addition to landscape complexity in Switzerland. Species richness of hoverflies increased with additional SNH at the landscape scale. However, the ubiquitous and dominant aphidophagous species Episyrphus balteatus was indifferent to landscape composition. Species richness of total and aphidophagous hoverflies was higher in woody than in herbaceous SNH. Hoverfly species richness was similar in linear and areal SNH, but non‐aphidophagous hoverflies were more vulnerable to landscape simplification in linear than areal SNH. Effects of the SNH type partly differed between the two countries. In Germany, the dominant aphidophagous species E. balteatus preferred woody over herbaceous SNH, while no such difference was found in Switzerland. Overall, local richness and abundance of floral resources were poor predictors for hoverfly abundance, richness or community composition. Synthesis and applications. Hoverfly species richness and community composition in semi‐natural habitats (SNH) were mainly driven by the SNH type and landscape complexity. Conservation and restoration of complex agricultural landscapes with a high proportion of different SNH types is therefore key for the conservation of hoverfly diversity, and thus likely to promote pest control and pollination services provided by them. Thereby, local improvement of SNH to promote hoverflies has to consider regional differences in habitat characteristics. [ABSTRACT FROM AUTHOR]