Predation rate of Hippodamia variegata (Coleoptera: Coccinellidae) feeding on different densities of Aphis gossypii (Hemiptera: Aphididae)

Predation rate is basic to any investigation of prey-predator interaction and a major component in the selection of predators for biological control. The predation rate of variegated lady beetle, Hippodamia variegata (Goze), fed on different densities (20, 40, 60, 80 and 100) of third instar nymphs of cotton aphid, Aphis gossypii Glover, was studied under laboratory conditions (25 ± 1 °C, 65 ± 5% RH and a photoperiod of 16L: 8D h). The net predation rates (C0) using age-stage, two sex life tables for 20, 40, 60, 80 and 100 aphids were calculated as 1547.50, 4011.91, 4450.78, 5300.20, 5305.73 prey nymphs, respectively. The mean consumption rates for male and female predators increased as prey density increased. The predation rate for both sexes also increased with increasing prey density. The lowest and highest predation rates for female were 1547.50 and 5305.73 prey nymphs at densities of 20 and 100 aphids, respectively. The transformation rate from prey population to predator offspring (Qp) decreased as prey density increased. It was concluded that any increase in the density of third instar nymphs of A. gossypii will result in significant effects on predation parameters of H. variegata.