Different modes of administration of dsRNAs for RNA interference. External application of RNAs by soaking or feeding bacteria requires the dsRNAs to cross the intestinal barrier and the siRNA signal to spread systemically. In some species octopamine is required to induce feeding behavior or electroporation may be used. Injection into the body cavity only requires systemic spreading of the signal. Internal application by injection into the syncytial female gonad ensures transmission to the next generation, regardless of systemic spreading. Intestine is in red, gonad in green.