Simple Estimation of Intrinsic Increase Rates for Aphids and Tetranychid Mites

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Abstract
A simplified method for the estimation of the intrinsic rate of natural increase (rm) of aphids is proposed. Having determined the prereproductive time, d (birth to 1st reproduction), the number of progeny (Md) produced in an equal time is observed and the rm is calculated from the equation: rm = 0.74 (logeMd)/d. The accuracy of the method is tested by reference to the life table data for 7 aphids under 8 sets of environmental conditions (Wyatt and Brown 1977) and by comparison with other published data. The method is shown to be equally applicable to tetranychid mites. It is suggested that a reasonably accurate estimate of generation time is provided by the value 4d/3.