Influence of Three Aphid Species for Determining the Stage-specific Functional Response of the Coccinellid Beetle Menochilus sexmaculatus (F.)

Abstract

Coccinellids are common predators of aphids, including Aphis nerii, Diuraphis noxia and Lipaphis erysimi. The zigzag ladybird beetle, Menochilus sexmaculatus, is an effective predator against various aphid species. In the present study, different stages of M. sexmaculatus were evaluated for their functional response against A. nerii, D. noxia, and L. erysimi. Functional response at different densities of aphids was calculated over a period of 24h at 25 ± 5 °C and 65 ± 5% RH. Roger's Random Predator equation was used to calculate the parameters of a functional response. All the predatory stages showed Type II functional response. Attack rate was highest in the fourth instar for all aphid species (4.5171, 2.5894 and 2.8853, respectively), while the shortest handling time of the fourth instar was recorded for A. nerii (0.0175h) and L. erysimi (0.0159h). In the case of D. noxia, the shortest handling time was observed in the first instar (0.0175h). The fourth instar of M. sexmaculatus consumed more prey, followed by the third instar. These results indicate that the fourth instar of M. sexmaculatus was the most effective stage against its prey, followed by the third instar, adult females and males. Further field experiments must be carried out to corroborate the efficacy of these predatory beetles under natural conditions.