Assessment of the functional response parameters of Coccinella septempunctata to varying densities of Acyrthosiphon pisum

The functional response of a predator describes the rate at which it kills its prey at different prey densities and is, therefore, an important tool to determine the efficiency of a predator in regulating the population dynamics of a prey. We investigated the functional response of Coccinella septempunctata L. (Coleoptera: Coccinellidae) to varying densities of Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae). The results revealed that the linear coefficient, P-1 in the reduced logistic model was found significantly negative for the 4th instar larvae and adult male and female of C. septempunctata (-0.002, -0.004 and -0.002, respectively) indicating a type II functional response. The parameter estimates of adult male, female and 4thinstar larvae of C. septempunctata calculated through Holling's disc model revealed that the highest attack rate (a) (1.047 +/- 0.014), shortest handling time (T-h) (0.0984 +/- 0.024 h) and largest maximum capture rate (T/T-h) (243.902) was exhibited by female. Parameter estimates calculated through Rogers's equation also showed the same sequence where maximum attack rate (a) of 0.00256 +/- 0.0003 was exhibited by female followed by 4th instar larvae (0.00251 +/- 0.0005). The shortest handling time (T-h) (0.210 +/- 0.003 h) and highest maximum capture rate (T/T-h) (114.17) was also exhibited by female. Comparison of functional response curves of adult male, female and 4th instar larvae revealed that maximum consumption of prey at all the densities offered was shown by female followed by 4thinstar larvae. The study manifested that C. septempunctata could be an efficient biocontrol agent of pea aphid, A. pisum.