A scientific note on the dynamics of labor devoted to nectar foraging in a honey bee colony: number of foragers versus individual foraging activity

Abstract

entered the hive and both the departure and arrival times of the trips were recorded. A nectar forager was defined as a bee that, after a trip of 10 min or longer, unloaded at least once a day liquid to a receiver bee. Between 0 and 67% of the workers engaged in nectar foraging on a given day, with a mean of 34 ± 18% per day. The percent nectar foragers in the colony changed significantly between days in 5 of 6 observation periods (Fig. 1), most likely as a reaction to changing nectar availability. Overall, 66% of the nectar foragers made 1–4 foraging trips per day, 34% made 5–10 trips, and no bee made more than 10 foraging trips per day. The mean number of trips per nectar forager per day was 3.5 ± 1.3. The majority of the nectar foragers (over 70%) foraged for 4.5 h or less, even though there were approximately 15 h of daylight each day. The mean activity level (number of foraging trips.bee–1.day–1) of the nectar foragers in the colony changed significantly between days in only 1 of the 6 observation periods (Fig. 1). The results of this study suggest that the honey bee colony adjusted its daily foraging effort mainly by changing the number of nectar Division of labor is common to all insect societies and is regarded as one of the most important factors in their ecological success. A key feature of the division of labor in insect colonies is its plasticity. Changing the labor effort devoted to a task with regard to its urgency enables a colony to respond adaptively to changes in external and internal conditions [1, 2]. Honey bee colonies (Apis mellifera) can be expected to adjust the labor devoted to nectar foraging, because foraging conditions strongly fluctuate. The proportion of a colony’s workers engaged in nectar foraging and the activity of each nectar forager are two parameters that might be involved in the adjustment [2]. In this study we measured for the first time both the proportion and the activity of nectar foragers in a honey bee colony. From May to July 1999, 6 random samples of each 50 bees were taken from a colony with about 4 000 bees that was housed in a 3-frame observation hive. The bees in each sample were individually marked, and observed over a period of 3 successive days (except the first period lasting 2 days). Observations started at 05.00 and lasted without interruption until 19.00–21.00 or until foraging activity stopped. Scientific note