The nymph of the damselfly, Enallagma civile, feeds on the larvae of the mosquito Culex tarsalis amongst a variety of other small aquatic invertebrates. Average daily consumption of 3rd instar Cx. tarsalis larvae by the last nymphal stage of E. civile was 6.06 larvae (range 4.64-8.67). Experiments in which density of prey (mosquito larvae) and predators (E. civile nymphs) were varied, showed that more prey was consumed as prey density increased. However, fewer prey were consumed at higher predator densities; mutual interferences among predators at higher predator densities was suspected.