The predators, Hydrophilus triangularis (Say) and Dytiscus marginalis were offered Culex quinquefasciatus larvae at densities of 4, 12, 36, 80, 120 and 200. With one exception, a greater number of mosquito larvae were eaten when the beetle larvae were hungry and more mosquito larvae were consumed when more were available. Although there was some variability in the data which may have been simply due to chance, D. marginalis was consistently more effective than H. triangularis.