Larval growth recorded as accumulation of protein was measured in Aedes aegypti, Culex nigripalpus and Culex quinquefasciatus, raised on liver powder or dry brewer's yeast. In the early stages all 3 species grew faster on liver powder, but at pupation there was no significant difference in protein content between diets and among species. Aedes aegypti pupated one day ahead of Culex.