Arrhenotoky, in which females arise from fertilized eggs and males from unfertilized eggs, has evolved multiple times inanimals, most prominently in the insect order Hymenoptera. An alternative form of haplodiploidy, in which females are haploid and malesdiploid—here named enantiotoky—is not known to exist. An illustrated thought experiment shows that if it does evolve, it will be veryunstable and is expected to disappear very quickly.
