Area dependent searching efficiency of Scymnus syriacus (Col.: Coccinellidae) feeding on Aphis craccivora (Hem.: Aphididae)

Searching efficiency is a key parameter of functional response which is in turn the major components in the selection of predators and parasitoids for biological control. Searching efficiency of Scymnus syriacus Mulsant feeding on Aphis craccivora Koch was determined at five different experimental arenas (i.e. ۱۹۵, ۲۴۷, ۳۰۴, ۳۸۵ and ۶۵۰ cm۲) on broad bean (Vicia fabae L.). To do this, functional response of the predator to different densities (i.e., ۱۰, ۲۰, ۳۰, ۴۰ and ۶۰) of the third instar nymphs of A. craccivora was studied. At each experiment, one ۴۸-h.-old female was introduced to the aphid density in a container (as an experimental arena) and replicated five times. The experiments were carried out at ۲۵˚ ± ۱C, ۶۵ ± ۵% RH and a photoperiod of ۱۶L: ۸D h. Using the logistic regression, a type III functional response was determined for S. syriacus in the entire five experimental arenas. Searching efficiency was found to be area dependent as it decreased as the area of experimental arena increased. The maximum expected predation rates (T/Th) were ۴۸.۵۶, ۴۲.۴۴, ۴۰.۷۷, ۳۸.۰۹ and ۳۴.۸۸ in the five experimental arenas, respectively. The area searched as a function of prey density indicated that as prey density increased, the area searched by the predator decreased. It is concluded that the size of searching area and prey density, both influence foraging behavior of S. syriacus.

Keywords:

واکنش تابعی , Scymnus syriacus , قدرت جستجو , Aphis craccivora , صحنهی آزمایش , سطح جستجوشده