Estimating the intrinsic rate of increase of Tetranychus urticae: which is the minimum number of immature individuals to consider?

The relationship between the number of immature individuals of Tetranychus urticae used to calculate life table parameters (sex ratio, development time, immature survival and the intrinsic rate of increase) and the accuracy of such determinations has been estimated. Additionally, the approach used in this paper, which considers each female offspring as a separate replicate, has allowed statistical comparison of the parameters obtained. At least the first four eggs from 16 females should be followed up to completion of their development to prevent the occurrence significant differences for the selected parameters. However, our results indicate that optimal sample sizes are different for the different life table parameters considered and should adapt to the preset level of accuracy.