Marked differences in arthropod biomass and species richness between two types of Malaise trap

Concerns about insect decline have motivated the monitoring of terrestrial arthropods, often using Malaise traps. Since the types of Malaise trap vary widely, it is essential to understand the differences in the resulting number and composition of the arthropod catch. In this study, we compared the performance of two types of Malaise trap in capturing arthropods for biodiversity monitoring and ecological studies. We placed Bartak and SLAM traps in a paired design at increasing distances from a forest edge in vineyards in southwestern Germany. We measured arthropod biomass and used metabarcoding for species identification. Bartak traps caught 7.5 times higher biomass, but only 1.5 times more species compared to the SLAM traps. There was a significant difference in species composition, whereby highly mobile flying insect species, such as those in the order Diptera, strongly dominated the Bartak traps and ground-dwelling arthropods were better represented in SLAM traps. With increasing distance to the forest edge, species richness decreased similarly in both trap types. Our study shows that differences in trapping efficiency must be taken into account when comparing results from different, and that trap types can be chosen according to the focus of each study. Nevertheless, both trap types were able to detect the biodiversity pattern in our landscape in a similar way.