Haplo-diploidy can be found in the Insects, Arachnida and Rotifera; having evolved convergently at least 20 times throughout these groups, involving multiple mechanisms (Normark 2003). Subsequently the research involved in this thesis deals with simulation and model based investigations of the evolution/invasion of haplo-diploidy, in addition to a more lengthy investigation into its impacts on host-parasite coevolution. And it’s consequences on the red queen hypothesis (the evolution of sex and recombination in co-evolving species). Demonstrating a strong qualitative and quantitative impact of haplo-diploidy on the red queen hypothesis. Therefore, I argue the case for greater evolutionary interest in and of haplo-diploidy, and alternative genetic systems.