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.

Pitfall trapping is an approved self-sampling method for capturing epigeal arthropods for ecological and faunistic studies. Capture efficiency of pitfall traps may be affected by external factors and the design of the trap. Pitfall traps set in forests are usually protected with covers or wire grids, but the effect of these constructions on sampling efficiency as well as their practicability and necessity have so far received little attention. During the present study pitfall traps of four different designs (covers, wire grids, litter exclosure, open) were tested in terms of their efficiency in capturing ground-dwelling arthropods (Acari, Araneae, Carabidae, Formicidae, Isopoda, Myriapoda, Opiliones) in order to gain a better understanding of the applicability and reliability of pitfall traps in forests. The study was carried out in an oak-beech forest in Northwest Germany using a total of 40 pitfall traps (ten replicates per trap design). Generalised linear models indicated no significant differences in arthropods counts among catches of pitfall traps of the four different designs, except for woodlice. Ordination analyses (NMDS) and MANOVA revealed no significant differences in spider and carabid beetle species compositions of the catches. In contrast, for both these taxa there were significant differences in the body sizes of the individuals caught. We conclude that the catches of pitfall traps are little affected by their design. Furthermore, the litter layer and litter input have no effect on the capture efficiency and thus there seems to be no need to protect pitfall traps with covers or wire grids in litter rich forest habitats.