Foraging ranges of solitary bees

1. Habitat requirements of solitary bees include nesting sites, food resources and nesting material. We used translocation experiments to establish foraging distances and measured foraging trip duration to analyse how solitary bees cope with the distance between nesting sites and suitable food plants in different habitat types. 2. Maximum foraging distance between nesting site and food patch was 150-600 m for the 16 bee species examined. Foraging distance was correlated positively with body length. Mean foraging trip duration, measured for seven bee species, ranged from 6 to 28 min and was also correlated with body length. In a study of the polylectic species Osmia rufa, we found a significant decrease in foraging trip duration with increasing number of plant species. Logistic regressions showed that the oligolectic Megachile lapponica nested in trap nests with a probability of 50% if the distance between trap nest and food patch was less than 250 m. The oligolectic Chelostoma rapunculi utilized trap nests when the distance to the nearest food patch was less than 300 m. 3. These experiments showed that solitary bees have a rather small foraging range so local habitat structure appears to be of more importance than large-scale landscape structure. All requirements for sustaining viable populations must be within this range. Therefore, it is necessary to maintain and restore a dense network of habitat patches in landscapes to ensure long-term sustainability of wild bee diversity and their ecological function as pollinators.