The movement patterns of carpenter bees Xylocopa micans and bumblebees Bombus pennsylvanicus on Pontederia cordata inflorescences

The movement patterns of carpenter bees (Xylocopa micans) and bumblebees (Bombus pennsylvanicus) foraging for nectar on vertical inflorescences of Pontederia cordata were studied near Miami, Florida. The floral biology of P. cordata is unique in several ways: (a) many short-lived flowers per inflorescence, (b) constant nectar production throughout the life span of each flower, and (c) absence of vertical patterning of nectar and age of flowers. Inflorescences ranged between 3.5 and 15.8 cm long and had between 9 and 55 open flowers. Both carpenter bees and bumblebees arrived mostly on the bottom third of the inflorescence and left after visiting flowers on the top third of the inflorescence. The departure position from the inflorescence was higher up than observed in studies of other insect pollinators foraging on other speces of plants. This pattern of departure probably occurs in the absence of a vertical gradient of nectar or floral morphology.