In haplodiploid species, like bees and wasps, females control the sex of offspring by deciding whether or not to fertilize each egg. If she fertilizes the egg, it will become diploid and develop as a female. If she does not fertilize the egg, it will remain haploid and develop as a male. In an elegant experiment, researchers showed that female "N. vitripennis" parasitoid wasps altered the sex ratio in their offspring in response to the environmental cue of eggs laid by other females.