Study area and bee species
This study was conducted between June and September 2016 in southern Wisconsin, in an area of experimental and traditional agriculture and suburban development. We selected three sites based on qualitatively distinct plant species diversity. At each of these sites we placed one honey bee, Apis mellifera , and one bumble bee, Bombus impatiens , hive. Individual honey bee and bumble bee hives within a site were separated by 60-100m (site 2: 60m; at sites 1 and 3: 100m). The distance between hive pairs among sites ranged from 700-1500m (sites 1-2: 700m; sites 1-3: 1500m; and sites 2-3: 1400m). Honey bees were housed in a two-frame wooden observation hive consisting of approximately 2000 workers and an actively laying queen. The bottom frame of each honey bee hive consisted of open and closed brood cells covering approximately half the frame, while the top frame was at least half covered in honey stores. The remaining cells were a mixture of empty cells or bee bread. Each hive was placed in a 1.2m3 wooden box with an exit tunnel providing access outside. Bumble bee colonies (Koppert Biological Systems, Howell, MI, USA) consisted of approximately 75 workers at the beginning of the experiment, and each hive was housed in a small wooden shelter located 0.5m off the ground.