Sexual selection in Apis bees

Honey bees in the genus Apis share many reproductive features with other social insects, but have also a number of highly derived mating characteristics, such as obligatory polyandry and - in at least two species - males who deposit their ejaculates directly into the spermathecal duct. These characteristics make the honeybees highly interesting and a special model system for studying sexual selection. Furthermore, the numerical sex ratio of Apis bees is extremely male biased and males die during their first and only copulation. This review updates our present knowledge of the mating biology of Apis bees and places this information into a broader concept of sexual selection. I concentrate on two intensively studied aspects of sexual selection: Sperm competition and cryptic female choice. I present evidence that sperm competition is likely to occur during the egg fertilization process, whereas cryptic female choice is likely to operate shortly after insemination when ejaculates of many males get stored in the spermatheca of the queen.