Larval age-specific searching efficiency of Aphidoletes aphidimyza (Dip.: Cecidomyiidae) preying on different densities of Aphis craccivora (Hem.: Aphididae)

Searching efficiency (a'') (attack rate) and handling time are two major components of natural enemies’ functional response and are usually used to evaluate their effectiveness. The age-specific searching efficiency of Aphidoletes aphidimyza (Rondani) was studied during its larval stage. The experiment was conducted in terms of age-specific functional response to the varying density (5، 10، 20، 40، 60 and 80) of third instar nymphs of Aphis craccivora (Koch) at 23 ± 1 °C، 70 ± 5% R. H. and a photoperiod of 16:8 h (L: D). Parameter estimates for logistic regressions showed a type III functional response at all larval ages to the varying density of A. craccivora. The age-specific handling times (Th) were estimated using Rogers random-attack equation، varied with the age of larval predator. The searching efficiency showed a similar and increasing trend at all predator larval ages. The estimated maximum rates of predation (T / Th) for the total larval stage were inversely related to prey density. It was concluded that A. aphidimyza، with type III functional response in all its larval stage، could be considered as a highly effective biological agent in suppressing and regulating A. craccivora population.