Life tables of Bactrocera cucurbitae (Diptera: Tephritidae): with an invalidation of the jackknife technique

Life table gives the most comprehensive description on the survival, stage differentiation and reproduction of a population and is thus the most important basis of population ecology and pest management. In this study, we constructed life tables for Bactrocera cucurbitae on cucumber (Cucumis sativus L.) in the laboratory and under simulated field conditions. To assess the variability of the life tables, we carried out two experiments under each treatment. Means, variances and standard errors of life table parameters were estimated for each of the two experiments by using the jackknife technique. At 25 degrees C, the intrinsic rates of increase (r) found for the two experiments were 0.1354 and 0.1002 per day, and the net reproductive rates (R0) were 206.3 and 66.0 offspring, respectively. For cucumbers kept in the field and covered with leaves, the r and R0 for the two experiments were 0.0935 and 0.0909 per day, and 17.5 and 11.4 offspring, respectively. However, if cucumbers were kept in the field but were not covered, the r and R0 for the two experiments were 0.1043 and 0.0904 per day, and 27.7 and 10.1 offspring, respectively. Our results revealed significant variability between the experiments under both laboratory and field conditions; this variability should be taken into consideration in the data collection and application of life tables. However, our mathematical analysis shows that the application of the jackknife technique will result in biologically unrealistic R0,i-pseudo and consequently overestimation of the variance of R0. According to our analysis, we suggest that the jackknife technique should not be used for the estimation of variability of the net reproductive rate.