Larvae of the predatory mosquito Toxorhynchites rutilus prey upon other container-dwelling insects, including larvae of the mosquito Ochlerotatus triseriatus. Previous work has established that O. triseriatus reduces movement, foraging, and time below the surface, and increases the frequency of resting at the surface, in the presence of water-borne cues to predation risk from T. rutilus. It is unknown whether concentrations of these water-borne, presumably chemical, cues in the environment influence these changes in behavior. Such an effect of concentration of predation cues could result in graded anti-predatory behavioral responses that adjust potentially costly behavioral changes to levels that are commensurate with the risk of predation. Behavior of 4th instar O. triseriatus was recorded in a series of concentrations (100, 10, 1, 0.1, and 0.01%) of water that had held either O. triseriatus larvae alone (Control) or that had held T. rutilus larvae feeding on O. triseriatus (Predation). Activity and position of larvae were recorded in 30 minute instantaneous scan censuses. Principal component scores summarizing frequency of movement, foraging, and time below the surface decreased significantly with greater concentration for the predator water, but not for the control water, indicating a graded behavioral response to water-borne cues to predation. There was a significant interaction of treatment and concentration, indicating that slopes of behavioral scores vs. concentration differed between treatments. Thus, at least for order-of-magnitude reductions in the concentrations of water-borne cues to predation, O. triseriatus is capable of adjusting its degree of behavioral response to the apparent risk of predation.