The functional response of Aphidius ervi to different Sitobion avenae densities on two wheat cultivars (Sardary and Alvand) was examined in laboratory conditions. Experiments were carried out in test tubes on an F2 lab generation without wheat clusters and also on F2 and F5 generations in pots using wheat clusters. In the tubes, female wasps were exposed to aphid densities of 2, 4, 7, 14, 28, 3...