The swarming behavior of the Sicilian honeybee (Apis mellifera sicula)

The reproductive behavior of this honeybee is different from all other European mellifera races. In the swarming season the colonies produce a high number of queen cells, and many virgin queens live together in the old and new colonies (Ruttner, 1988). In the spring of 1992, we investigated 9 bee hives near Trapani (western Sicily). The hives were supplied with extra food and were controlled daily as follows: the mother queens' intention to swarm was estimated by observing their egg production and motor activity. The new queens were marked individually by numbered opalith-platelets to determine their lifespan. In addition, we were able to investigate the reactions of the worker bees in the polygynous phase and the aggression between the queens. Two d after swarming, the queens were counted and their behavior in the new colony observed. As expected, the bee colonies showed a high production of queen cells, with a maximum of 232 capped cells in 1 d (see fig 1). The number of emerged queens varied from 1 to 33 individuals per d. In the old colonies the new queens were killed by workers or sister queens within 2 d (see fig 2). Many queens got lost during the swarming process. One prime swarm was observed; in 5 other colonies the mother queens were killed before swarming. This seems to be typical of the Sicilian honeybee. Worker bees showed no strong aggression to virgin queens in the old colony; even foreign queens that entered the hive were tolerated. In the swarm clusters the worker bees showed little interest towards individual queens. If queens fell out of the cluster, only a few bees reacted, and the queens were tolerated when they returned to the swarm. The entire swarm returned to the hive when < 3 queens were in the cluster. Swarms can associate with other swarms, including foreign swarms, or can split into sub-swarms. In the new colonies we observed 2 to 13 coexisting queens (see fig 3). The duration of survival of the virgin queens was limited to 2 to 3 d. Nearly 70% of the queens were killed during this period of time. Usually, the worker kees killed the queens by balling. Before the mating flights, which started at age 6-10 d for the queens, nearly all new colonies were again monogynous. Survival of the new queens in old and new colonies was found to be in accordance with earlier laboratory tests. In these tests 2 virgin sicula queens were caged together with 20 worker bees (Tiemann et al, 1991). Queens at age 2 d showed a significantly higher aggression rate (P ≤ 0.05) than queens at age 1 d (Tiemann and Brückner, 1992). We assume that the change in aggression rate was caused by the increase in concentration of one or more pheromones. It was thought that the Sicilian honeybee remained polygynous until the mating flights had been completed (Ruttner, 1988; Engels, 1990). We observed aggressive behavior between queens and workers independent of the mating flights and long before they took place. Further investigations are planned to determine which pheromones change within 2 d in the virgin queens and whether a special pheromone pattern exists in the Sicilian race which is different from that of other European races