Trophallaxis in filled-crop honeybees (Apis mellifera L.): food-loading time affects unloading behaviour.

Honeybees ingested 50% w/w (1.8 M) sucrose solution at a rate feeder offering either 16.5, 32.5 or 65 microliters/min. While the time spent ingesting solution at the feeder decreased significantly with increasing flow of solution, bees attained maximum crop loads with this range of flows. Different parameters related to mouth-to-mouth food exchange (trophallaxis) showed important modulations as the offered flow of solution was incremented. Trophallactic transfer rate, i.e. the speed at which liquid food is transferred from donor to recipient bee, was found to increase along with increasing profitability at the rate feeder. In the present case, food source profitability could have been evaluated by foragers either by measuring the time invested in ingesting the solution, or by direct assessment of the flow rate of the feeder. Thus it seems that perception of profitability conditions at the food source suffices for later representation in the hive through trophallactic contacts, independently of crop-filling state.