To be on the safe site – Ungroomed spots on the bee’s body and their importance for pollination

Flower-visiting bees collect large quantities of pollen to feed their offspring. Pollen deposited in the bees' transport organs is lost for the flowers' pollination. It has been hypothesised that specific body areas, bees cannot groom, serve as 'safe sites' for pollen transfer between flowers. For the first time, we experimentally demonstrated the position, area and pollen amount of safe sites at the examples of Apis mellifera and Bombus terrestris by combining artificial contamination of the bees' body with pine or sunflower pollen and the subsequent bees' incomplete grooming. We found safe sites on the forehead, the dorsal thorax and waist, and on the dorsal and ventral abdomen of the bees. These areas were less groomed by the bees' legs. The largest amount of pollen was found on the waist, followed by the dorsal areas of thorax and abdomen. At the example of Salvia pratensis, S. officinalis and Borago officinalis, we experimentally demonstrated with fluorescent dye that the flowers' pollen-sacs and stigma contact identical safe sites. These results confirm that pollen deposition on the bees' safe sites improves pollen transfer to stigmas of conspecific flowers sti. Future research will demonstrate the importance of safe sites for plant pollination under field conditions.