The fertilization process is a female decision. The female stores the male sperm for later fertilization of eggs. All bees and wasps, including parasitoid wasps are haplodiploid. This means not all eggs have to be fertilized to develop. Unfertilized eggs become males, which are haploid .
Fertilized eggs become female, and are diploid .
In autoparasitoids, placement is also important in sex development. Female eggs can only develop on whitefly larvae. This makes the whitefly a primary host, meaning that the wasp generally places its eggs on this host. The humans from the Aliens movies are the primary host for the aliens. Male wasps can only develop on wasp larvae.