While most insects will feed from many kinds of flowers, there are certain specialists in both groups. Some insects have adapted to feed efficiently from just one species of flower, and some plants have evolved flower structures that encourage pollination only by certain kinds of insects. For example, open, upright flowers are favored by butterflies, while low, drooping flowers are pollinated by bees. The nectar at the base of a long, trumpet-shaped flower is more accessible to a butterfly than to short-tongued bee. Some short-tongued bees have a trick for reaching this nectar, however: they cut small holes at the base of the flower, so they can drink the nectar directly instead of reaching through the flower. But this is of no advantage to the plant, because nectar is consumed with no movement of pollen. Red clover is pollinated mostly by large bumble bees, while the smaller white clover flowers attract honey bees, whose tongues are too short to reach the nectar within red clover flowers.