Abstract: This study was conducted to study predatory efficiency and functional response of females diving beetles, Dineutus aereus, when feeding on different densities of second and fourth stages of mosquitoes Culex pipiens larvae . . Larval and pupae stages of mosquitoes were treated with predators. Results were observed 24 after treatment,tests were conducted at temperature at 25 ± 2 °C and humidity of 65% ± 5 and 12 hours of illumination, the water beetles of D.aereus showed the maximum average consumption of 219.2 ± 15.23 larva / day for larval stage while the pupae stage showed less consumption than the rest of the stages with an average consumption of 69.6 ± 3.19 larva / day