We examined how mosquito life history parameters and whole body carbon (C), nitrogen (N), and phosphorus (P) content responded to changing C, N, and P content in food. The southern house mosquito, Culex quinquefasciatus Say, and the western encephalitis mosquito, Cx. tarsalis Coquillett, were reared in containers with diary waste water (high food and C, N, and P concentrations) or effluent from a constructed wetland (low food and C, N, and P concentrations). Low food density decreased survivorship and delayed development from hatching to eclosion and reduced adult mass for both species. Adult females were always heavier than adult males, and Cx. tarsalis adults were heavier than Cx. quinquefasciatus adults. There was little change in C, N, and P content for Cx. quinquefasciatus adults across food treatments, whereas Cx. tarsalis was more variable in C and P, but there was little change in N. Adult Cx. quinquefasciatus had a higher P content (3.0%) than Cx. tarsalis (2.0%). Compared with other aquatic and terrestrial taxa, the relatively high percentage of N and P content (11.5 and 2.5%, respectively) of adult mosquitoes suggest an evolutionary trend toward rapid rates of growth, especially for species that use highly enriched habitats as developmental sites.