Prey Preference of Hippodamia variegata (Col.: Coccinellidae) on two aphid species: Lipaphis erysimi and Brevicoryne brassicae

Prey preference of natural enemies is one of the phenomena that should be considered to study the efficiency of natural enemies. When the predator has a choice between two or more preys, they often show preference for one of them. Two species of aphids, Brevicoryne brassicae and Lipaphis erysimi, could cause serious damage on crusiferan plants. Hippodamia variegata is one of the main predator of these aphids. This experiment was conducted to determine the feeding preference of fourth instar larvae of ladybeetle, H. variegata on two mentioned aphids species. Experiment was done in Petridishes containing Canola leaves for 24 hours. In this study, prey-preference of H. variegata was tested on canola plants at laboratory conditions (25±1°C, 70±10% RH, and 16:8 L:D Photoperiod). They were observed after 24 h to record the number of surviving aphids from each type of prey. Predator preference was analyzed using the Manly’s index of preference. Results showed that the forth instar larva ate 70.4±5.13 L. erysimi and 60.25±4.39 B. brassicae during the test time. Based on collected data, preference index were 0.592 and 0.408 on L. erysimi and B. brassicae, respectively. In switching experiment, five different densities of the two aphid species were offered to the predator and result showed that all the ratios of L. erysimi and B. brassicae had no effect on the preference of forth instar larvae of ladybeetle H. variegata.