<p>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.</p> <p>Counting individuals of Arion rufus [Linnaeus] within 400 m^2 in 19 Plots in the Hainich. Centre of the plot is the original plot centre of the GPs.</p>