Functional and Numerical Responses ofScymnus SyriacusMarseul (Coleoptera: Coccinellidae) to the Black Bean Aphid,Aphis FabaeScopoli (Hemiptera: Aphididae) Under Laboratory ConditionsFunctional and numerical responses are basic to any investigation of predator-prey relationships and key components in the selection of predators for biological control. In this study, functional and numerical responses of the female and male ladybeetles,Scymnus syriacusMarseul to different densities of third instar nymphs ofAphis fabae(i.e.5, 10, 20, 30, 40, 60 and 80) as prey, were studied in a growth chamber (25°C, 65±5% RH and a photoperiod of 16L : 8D h) on the broad bean,Vicia fabaeLinn. Using the logistic regression, a type II functional response for both female and male ladybeetles was determined. Using Nonlinear least-square regression, the searching efficiency (a') and handling times (Th) of the female and male adults were estimated as 0.123±0.006 h, 0.434±0.012 h and 0.115±0.008 h, 0.514±0.016, respectively. The Rogers model was used to estimate the maximum theoretical predations (T/Th) for female and male, which were 55.18 and 46.64, respectively. These results indicated a higher efficiency in female ladybeetles. The reproductive numerical response, in terms of eggs laid, increased curvlinearly with increasing prey density. The reproductive response trend was similar to the shape of the type II functional response. This similarity means both responses are interlinked and function simultaneously. The efficiency of the ingested food conversion (ECI) of the females decreased with prey density, as females laid 25±0.65 eggs when exposed to the highest prey density (80) and 3±0.44 eggs at lowest prey density (5).
Permanence of a Discrete Periodic Volterra Model with Mutual Interference
