We present a method by which RNAi by feeding is as strong and as sensitive as RNAi by injection for detecting embryonic phenotypes, and, furthermore, is more sensitive for detecting sterility and post-embryonic phenotypes. The fact that feeding is superior to injection for detecting sterile phenotypes is most likely due to the fact that with feeding the RNA interference effect is begun at L4 stage, giving it more time to affect the germline or gonad, whereas young adults are usually injected; nevertheless, this does not diminish the utility of feeding for detecting sterility as L4-stage hermaphrodites are considerably more difficult to inject. Similarly, the fact that feeding is better than injection for producing post-embryonic phenotypes could be due to the fact that both fed mothers and their progeny are constantly exposed to dsRNA, whereas by injection only the mothers are subjected to a single dose. Again, this confers an inherent advantage on feeding in producing post-embryonic phenotypes that can be exploited by those studying genes important later in development. It should be noted, however, that there are gene-specific differences between
