Instead, the bumble bee attacked the plant from the outside, carefully puncturing the long tail of the flower to get at the nectar, without going anywhere near the pollen. Most of the columbine flowers nearby had been punctured in the same place. Some bumble bee species have tongues long enough to reach nectar in the long spurs of columbine, and others don't. If you crouch in a bean field at dawn you can hear the snapping of the mandibles as primary robbers perforate the day's new flowers. Robbing behaviour is learnt.
Individuals often develop a habit of biting consistently on the left or right-hand side of a flower.
Jens Olesen showed that as the flowering season progressed, the bees got better at positioning their holes in the best place for access to the nectar. This process is termed nectar robbery and has been shown in Corydalis , a spurred flower. When flowering begins, bumblebees perforate various parts of the spurs at random, but after a few days they become more precise, biting the hole near the surface of the nectar. Other insects whose mandibles are too weak to perforate the flowers, such as hoverflies, indulge in secondary robbing, using the holes made by the bees. Nectar robbery is normally expected to have an adverse effect on plant reproductive success because the removal of nectar without effecting pollination forces the plant to produce more nectar.