Trap nests are a well established tool to monitor cavity-nesting Hymenoptera and to assess parasitism rates. Despite only 5-10% of all non parasitoid solitary bee and wasp species are colonizing trap nests, it has been show that the cavity-nesting part of the Hymenoptera community is representative for the overall community in terms of species richness and abundance. In the BEF-China project, we used standardized trap-nests in all 27 CSPs and in 51 plots in Site A. Per plot, two wooden posts with four trap nests, each consisting of a 22 cm long, 12.5 cm diameter plastic tube filled with dried Arundo donax L. (Poaceae) internodes of varying diameter (2-20 mm) were exposed. Trap nests were set up approximately 1.5 m above the ground and controlled monthly for nests that are easily distinguishable by the characteristic nest sealing pluck. A broad spectrum fungicide that is non-toxic to Hymenoptera (Folicur®, Bayer CropScience, Monheim, Germany) was applied monthly with a hand sprayer to prevent molding in the humid climate of the study site. Internodes containing nests were replaced with new internodes of the same diameter. Nests were taken to the laboratory, opened and reared in glass test tubes closed with cotton wool till hatching. We found a diverse set of bee, wasp, and parasitoid species. Individual species differ markedly in their nesting and feeding ecology. Here we show illustrate a few exemplary species in order to explain the principle of trap nests.