Journal of Vector Borne Diseases (Mar 2005)
Frequency-dependent prey-selection of predacious water bugs on Armigeres subalbatus immatures
Abstract
Background & objectives: The predatory behaviour with reference to the frequency-dependentprey-selection of the water bugs Sphaerodema annulatum Fabricius and S. rusticum Fabricius wasstudied in the laboratory using the IV instar larvae and pupae of Armigeres subalbatus as prey toascertain their efficacy as predator of mosquito immatures.Methods: Field collected adult morphs of the water bugs were allowed to predate on larvae and pupaeprovided in different ratios and densities as per the model of Greenwood and Elton1 for a fixed timeperiod. The data obtained on their predation rate were analysed with respect to the model parameters,lnV—the frequency independent component and b— the frequency dependent component of selection.Results: It was found that the prey-selection was dependent on the relative numbers of prey available,favouring apostatic selection. The b values and lnV values for S. annulatum were 0.54 + 0.01 and0.92 + 1.04 respectively whereas the corresponding values for S. rusticum were 0.71 + 0.03 and0.17 + 1.57 respectively.Interpretation & conclusion: The selection of preys by the water bugs was dependent on the relativenumber of the prey forms and thus they are expected to predate on the form more abundant in aheterogeneous prey population and adversely affect the adult emergence.
