(Julius-Maximilians-Universität) Pesticides, habitat destruction, climate change all contribute to bee mortality. But there could be another important factor to consider as well: the bacteria that live in and with bees. Many of them are important for the health of bees, and if they suffer, so do the bees. Until now, research has been based on the assumption that the knowledge gained from honey bees can be transferred to solitary bees – which is true only to a limited extent. So researchers have started to investigate the landscape ecological factors that influence the microbial associations of solitary bees as well.