Relationship of number of food-plant species recorded per bumblebee species to number of bee records per bumblebee species.

For species of the subgenera Megabombus (black spots), Pyrobombus (triangles), Melanobombus (circles), and Bombus s. str. (squares). Species with few food-plant-species records relative to the number of bee records are interpreted as more specialised in their fewer food-plant choices (Data from Sichuan [13]).