The phenomenon of thelytoky, the asexual production of diploid female offspring, is being increasingly uncovered among the eusocial Hymenoptera. Thelytoky is associated with a number of fascinating and novel reproductive systems. In this thesis I investigate the evolutionary and genetic consequences of thelytokous parthenogenesis, with particular focus on the Cape honey bee Apis mellifera capensis (hereafter Capensis). In Capensis thelytoky is associated with loss of heterozygosity, which can only be curtailed by ongoing selection against homozygous offspring. This selective cost is one factor that drives the distribution of thelytokous reproduction within the Capensis population, as different castes differ in their ability to endure the costs, and capitalise on the benefits of thelytoky. Considering these costs and benefits in a broader context, I show that the distribution of thelytokous parthenogenesis across the eusocial Hymenoptera can be accounted for by the constraints imposed by caste conflict within an insect colony.