We are more than grateful to Ingemar Fries of the Swedish University of Agricultural Sciences for comments on and contributions to earlier versions of the chapter. We thank K L Crous and A A Yusuf for comments on an earlier version of the manuscript and we also thank Werner Luginbühl for a very thoughtful and thorough review of the original submission. The University of Pretoria, the National Research Foundation of South Africa and the Department of Science and Technology of South Africa (CWWP) granted financial support. The COLOSS (Prevention of honey bee COlony LOSSes) network aims to explain and prevent massive honey bee colony losses. It was funded through the COST Action FA0803. COST (European Cooperation in Science and Technology) is a unique means for European researchers to jointly develop their own ideas and new initiatives across all scientific disciplines through trans-European networking of nationally funded research activities. Based on a pan-European intergovernmental framework for cooperation in science and technology, COST has contributed since its creation more than 40 years ago to closing the gap between science, policy makers and society throughout Europe and beyond. COST is supported by the EU Seventh Framework Programme for research, technological development and demonstration activities (Official Journal L 412, 30 December 2006). The European Science Foundation as implementing agent of COST provides the COST Office through an EC Grant Agreement. The Council of the European Union provides the COST Secretariat. The COLOSS network is now supported by the Ricola Foundation - Nature & Culture.