Simple estimation of instrinsic increase rates for aphids and tetranychid mites.
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 first 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 four aphids under eight sets of environmental conditions and by comparison with other published data. The method was shown to be equally applicable to tetranychid mites, by reference to published data. It is suggested that a reasonably accurate estimate of generation time is provided by the value 4d/3.