Functional responses of coccinellid predators: an illustration of a logistic approach.

The functional response parameters and patterns of three coccinellid predators, Cheilomenes sexmaculata, Propylea dissecta, and Coccinella transversalis (Coleoptera: Coccinellidae) were evaluated to find out how these predators respond at two different prey species across various prey densities levels. All three predators exhibited a decelerating curve Type II response determined by a logistic regression model. The linear reciprocal transformation of Holling's disc equation was used to further evaluate the parametric values. C. sexmaculata responded maximally, followed by C. transversalis and P. dissecta, in terms of consumption of the aphids, Aphis craccivora and Myzus persicae, with suitable values of coefficient of attack rates and handling times on these prey species. Differences in handling times were found to be significant within and between the predatory species on both prey species indicating that predators respond differentially to prey species. Differences in coefficients of attack rates, however, did not vary significantly in most of the treatments. The potential role of these predators in biocontrol of A. craccivora and M. persicae suggests that C. sexmaculata is the best predator for the management of both prey species, particularly A. craccivora. However, further field based studies are needed to confirm this hypothesis.