Apparent preference by bees for different flower colours in cowpeas (Vigna sinensis (L.) Savi ex Hassk.)

Summary A strong preference for different cowpea flowers apparently due to colour is reported for bumble bees (Bombus spp.) and honey bees (Apis mellifera). Bumble bees visited purple flowers much more often than they did white flowers in a ratio of 3:1. Honey bees, on the other hand, visited white flowers more than they did purple flowers in a ratio of 2:1.Judged from the positioning of their heads in the flowers, bumble bees are generally nectar collectors while honey bees collect both pollen and nectar but more of the former.This strong preference has implications in experiments designed to estimate out-crossing where different flower colours are used in the detection of hybrid plants. There will be more intra-colour than inter-colour pollen transfer.