Soodeh Davoodi Dehkordi - Department of Plant Protection, Faculty of Agriculture, University of Guilan, Rasht, Iran
Ahad Sahragard - Department of Plant Protection, Faculty of Agriculture, University of Guilan, Rasht, Iran.
Jalil Hajizadeh - Department of Plant Protection, Faculty of Agriculture, University of Guilan, Rasht, Iran.

The functional responses of one and two individual female predators, Hippodamia variegata Goeze (Col.:Coccinellidae) to different densities of third instar nymphs of Aphis gossypii Glover (Hem.: Aphididae) werecompared in a growth chamber (25˚C, 65 ± 5% RH and a photoperiod of 16L: 8D h). The black eyed bean,Vigna unguiculata leaves were used as host plant for aphids. Each experiment was replicated ten times.Using logistic regression, a type II functional response was determined for female ladybeetles in both cases.The searching efficiency (a') and handling times (Th) of the female by using nonlinear regression wereestimated as 0.0402 ± 0.00180 h-1 and 0.0333 ± 0.0167h, 0.0421± 0.000940 h-1, 0.0105 ± 0.0320 h for two andone individuals of female predator, respectively. It is concluded that the number of predator individuals hadno influence on the type of functional response of the predator to different densities of its prey.

Hippodamia variegata, Aphis gossypii, Functional response, Two individual predators