Foraging loads of stingless bees and utilisation of stored nectar for pollen harvesting

We compared nectar, pollen and resin loads of individual workers among colonies from six Trigona species in Sabah, Borneo. Individual bees rarely collected large amounts of both nectar and pollen during the same foraging trip. Instead, comparison of crop contents across departing, flower-visiting, and returning bees suggests that pollen-collecting workers often carried highly concentrated nectar in their crop upon nest departure. During their foraging trip, this crop nectar volume decreased progressively until crops were largely empty when they returned to their nest. Individually marked pollen foragers carried highly concentrated nectar when they left their nest, while crops and corbiculae from marked nectar foragers were empty upon departure. We suggest that a large proportion of previously stored and highly concentrated nectar may be required for pollen adhesion to corbiculae and/or serve as fuel during foraging on nectarpoor flowers.