) APHIS CRACCIVORA( و شته اقاقيا )APHIS NERII( نسبت به تراكم هاي مختلف دوگونه شته خرزهره )COL: COCCINELLIDAE( EXOCHOMUS NIGROMA CULATUS واكنش تابعي كفشدوزك

Functional response of Exochomus nigromaculatus (Col.: Coccinellidae) to different densities of Aphis nerii and Aphis craccivora

The functional response of the lady beetle, Exochomus nigromaculatus, was examined at different densities of Aphis nerii and Aphis craccivora under laboratory conditions (30 ±1 °C and 65±5 %RH, with a 14:10 L;D photoperiod). For each experiments, a piece of host plant and a given density of prey and one predator were placed in a Petri dish. After 24 hours, the total number of prey attacked was counted and experiments conducted in 5 replicates. The results revealed that, 4th instar larvae and adult of E. nigromaculatus exhibited a type II functional response to density levels of 4, 8, 16, 32, 64, 96, and 128 aphid preys. A non-linear regression analysis (Least squars procedure) was used to estimate searching efficiency and handling time of predator. Searching efficiency and handling time of 4th instar larvae of the predator reared on A. nerii were 1.24 and 0.006, and for those reared on A. craccivora were 1.17 and 0.009, respectively. Searching efficiency and handling time of Adult predators reared on A. nerii were 1.12 and 0.007, and for those reared on A. craccivora were 1.01 and 0.008, respectively. The difference in prey species seems to have a contributing factor in determining the rate of predation, whereas searching efficiency in both stages of predator with prey of A. nerii was higher than A. craccivora.