Alexandra Jeuck1, Hartmut Arndt2. 1. Department of General Ecology, Zoological Institute, Cologne Biocenter, University of Cologne, Zülpicher Straße 47b, D-50674 Cologne, Germany. 2. Department of General Ecology, Zoological Institute, Cologne Biocenter, University of Cologne, Zülpicher Straße 47b, D-50674 Cologne, Germany. Electronic address: hartmut.arndt@uni-koeln.de.