Influence of density-dependent aphid consumption on the body-weight of a predaceous ladybird, Coccinella transversalis

Abstract

We investigated the influence of density-dependent aphid consumption on the body-weight of adult male and female ladybirds, Coccinella transversalis Fabricius when fed on aphid, Hysteroneura setariae (Thomas). This density-dependent prey consumption in terms of functional response seems to modulate the body-weight of adult ladybirds, which has a direct implication on the fate of aphid biocontrol. Hence, adult male and female ladybirds were fed on aphids at varying densities (10 to 200 aphids) and the magnitude of aphids consumed and their influence on the adult body-weight was recorded. The prey consumption increased with an increase in aphid density and the aphid consumption pattern exhibits a Type II response. This simultaneously affected the body-weights of adult male and female, C. transversalis, which increased from 0.59±0.08 to 2.72±0.35 mg, and 0.69±0.083 to 3.46±0.37 mg, respectively when fed on aphids at an increasing density from 10 to 200 aphids. Among adults, female was a more potent aphid-biocontrol agent, as it possesses a greater attack rate (0.8423 ± 0.18) and can handle prey in lesser time (0.1558 ± 0.02 hour or 9.35 ± 1.20 min), as compared to that of male ladybird. The density-dependent aphid consumption may directly affect the body-weight, as consumption of a greater number of aphids may lead to the increase in adult bodyweights, thereby making them better biocontrol agents in terms of quantitative aphid consumption. It is concluded that adult female C. transversalis possesses the potential for the biocontrol of H. setariae.