13.1. Introduction

As a member of the Hymenoptera, honey bees have haplo-diploid sex determination. This system of sex determination depends on a single sex locus. Thus inbreeding has a severe negative impact on the viability of the offspring. Thus, natural selection has favoured several behavioural mechanisms to prevent mating among related drones and queens. Altogether, the "general aim" of honey bee mating can best be understood as an optimized mode "of avoiding relatives".

Queens are able to regulate fertilization of an egg (Bresslau’s sperm pump) and thus, together with worker bees, regulate the number of drones per season. At the same time, worker bees can regulate the number of daughter queens by feeding them with royal jelly. Investment in queens, which need large numbers of worker bees for swarming (colony fission), is costly while drone production does not involve more than rearing and maintaining individual drones. The estimated sex ratio is about 1 queen to up to 2,000 drones. The absolute control of the production of "full" females and males combined with the high susceptibility of inbreeding is a unique character for Apis and results in a mating behaviour which is exceptional in several aspects.

For mating, drones and queens leave the hive and meet quite far away at special congregation areas high in the air, where they copulate in free flight. So far, mating cannot be achieved in confinement. Consequently, natural mating behaviour cannot be observed directly or controlled for. Nevertheless, several aspects of mating behaviour have been uncovered by indirect conclusions from flight behaviour at the flight entrance, dissection of queens and drones, watching drone behaviour towards fixed queens at a drone congregation area (DCA) and analysis of offspring. Drones are attracted by the queen's sex pheromones whose main component is 9-oxodec-2-enoic acid (9 ODA; Gary, 1962). While flying at the DCA the queen's sex pheromones are dispersed not only because of the flight pattern of the queen, but also by the flock of drones which pursue the queen from a short distance (Koeniger et al., 2011). Therefore, it is not only the sex pheromones that are important for mating behaviour, but the shape, colour and pattern of the queen dummy also play an important role (Gary and Marston, 1971; Koeniger, 1990; Vallet and Coles, 1993; Gries and Koeniger, 1996). Drones of all Apis species tested so far have reacted to a black wooden stick, 3.2 cm long, 0.5 cm in diameter, which was impregnated with 1 mg synthetic 9 ODA. Smaller black objects and a queen carcass also elicit drone pursuit when 9ODA is present. Sex pheromones seem to indicate the presence of a queen but close-by navigation is greatly influenced by the shape of the dummy.