INTRODUCTIONNasonia is a complex of four closely related species of wasps with several features that make it an excellent system for a variety of genetic studies. These include a short generation time, ease of rearing, interfertile species, visible and molecular markers, and a sequenced genome. Furthermore, its parasitoid lifestyle allows investigations of questions relating to parasitoid/host dynamics, host preference, and specialist versus generalist biology. It also can serve as a behavior model for studies of courtship, male aggression and territoriality, female dispersal, and sex ratio control. This protocol describes a method to use RNA interference (RNAi) to knock down genes in Nasonia larvae. Unlike in Drosophila, RNAi in Nasonia is systemic. In the example presented here, adult red-eye-color phenotypes are produced by injecting double-stranded RNA (dsRNA) against the eye color gene cinnabar into last-instar Nasonia larvae.