The phenomenon occurring in the reproduction of certain animals in which fertilized eggs give rise to females and unfertilized eggs to males. It is found among certain insect groups, notably the wasps and bees (Hymenoptera), and in mites, as well as rotifers and nematodes. The males are haploid and transmit only the maternal genome—their production represents arrhenotokous parthenogenesis—whereas the females are diploid. In pseudo-arrhenotoky both males and females arise from fertilized eggs and are diploid, but males subsequently become effectively haploid by inactivation of the paternal genome, either in all cells or only in germ-line cells. This occurs in certain scale insects and mites. Compare thelytoky.