Searching and Feeding Efficiency of a Ladybeetle, Coccinella transversalis Fabricius on Aphid, Aphis gossypii Glover

Abstract

Searching and feeding efficiency of a predaceous ladybird beetle, Coccinella transversalis Fabricius was investigated for brinjal aphid, Aphis gossypii Glover at varying predator and prey densities. Rate of prey consumption per predator decreased with increase in the number of predators, due to mutual interference (0.90) amongst the larvae. Searching efficiency (area of discovery) of fourth instar larvae decreased from 0.1846 to 0.0779 when one, two, four and eight predators were exposed to a constant prey density (200). Prey consumption by a single larva increased with increase in prey densities but the percent prey consumption decreased. Maximum percent prey consumption was noticed at the lowest prey density (50) and minimum at highest prey density (800). Searching efficiency of a fourth instar larva decreased from 1.7263 to 0.4727 with increase of prey density from 50 to 800 individuals of A. gossypii. The predator-prey ratio of 1:50 may be considered optimal for the augmentative release of C. transversalis for the biocontrol of A. gossypii.