Effect of different foraging periods on the functional response of Aphidoletes aphidimyza (Diptera: Cecidomyiidae) at different densities of Aphis craccivora

Searching efficiency and handling time are two major components of functional response and are usually used to evaluate effectiveness of natural enemies. The effect of different foraging periods on the functional response of larval Aphidoletes aphidimyza (Rondani) (Dip.: Cecidomyiidae) feeding on third instar nymphs of Aphis craccivora was studied. The experiment was conducted in terms of time-specific (۱, ۲, ۴, ۶,۱۲, ۲۴ h.) functional response to varying densities (۵, ۱۰, ۲۰, ۴۰, ۶۰ and ۸۰) of third instar nymphs of A.craccivora at ۲۳ ± ۱ °C, ۷۰ ± ۵% of R.H., and a photoperiod of ۱۶:۸ h (L: D). Parameter estimates for logistic regressions showed a type II functional response for ۴ day-old larvae of the predator at different foraging periods to varying densities of A. craccivora. The estimated searching efficiency (a') and handling times (Th), varied with foraging periods. The searching efficiency showed a decreasing trend as the foraging periods increased. The estimated maximum rates of predation (T/Th) for the ۴-day old larvae were directly related to the foraging periods increase but handling times (Th), showed a decelerating trend. In conclusion it was found that searching efficiency was a variable parameter in different foraging periods of A. aphidimyza and was lowest at the foraging periods of ۲۴ h. It was also suggested that A. aphidimyza with type II functional response in all foraging periods, could be considered as a highly effective biological agent in suppressing A. craccivora population.