Functional Response of Coccinella septempunctata (Coleoptera: Coccinellidae) to Different Species of Aphids (Hemiptera: Aphididae)

Stage-specific functional response of Coccinella septempunctata L. was evaluated under laboratory conditions to varying densities (10, 20, 40, 60, 80, 100, 120, 150 and 200) of Lipaphis erysimi (Kaltenbach)., Diuraphis noxia Kurdjumov. and Aphis nerii Fonscolombe. Logistic regression analysis of all life stages of C. septempunctata exhibited negative linear-coefficient (P1), confirming a curvilinear type II functional response against all the tested aphid species. The fourth instar of C. septempunctata, in comparison to other stages, exhibited the highest predation activity against D. noxia and A. nerii, with an attack rate (a) of 7.31 h-1, 5.79 h-1 and handling time (Th) of 0.0106 h, 0.0092 h, respectively. Under different densities of L. erysimi, adult females of C. septempunctata exhibited the highest predation activity with an a of 7.58 h-1, followed by the fourth instar with a of 7.31 h-1 and adult male 6.60 h-1 and Th of 0.0066 h, 0.0079 h and 0.0092 h, respectively. The attack rate and handling time estimated for different stages of C. septempunctata showed that the fourth instar of C. septempunctata had the highest attack rate, whereas handling time was variable. Adult females of C. septempunctata showed minimum handling time (0.00013 h) in most of the cases. Our results suggest that the fourth instar larvae and adult female of C. septempunctata are efficient predator for the biological control of L. erysimi, D. noxia and A. nerii. Further field-based studies are needed to confirm this hypothesis.