Original data comes from a project which takes or took place as part of the DFG priority program "Exploratories for large-scale and long-term functional biodiversity research". The data is stored together with descriptive metadata, in combination called a dataset, in the project repository (https://www.bexis.uni-jena.de). Species information was extracted from that original dataset. The second paragraph is part of the metadata of the original dataset. Flower availability is estimated by determining the number of 'flower units' across the grassland types of the Exploratories as a basis for analyzing flower-visitor interactions networks. We focus on resource-based mechanisms that may determine flower visiting insect communities in different habitats.