Comparative demography of group- and individually-reared life tables of papaya mealybug with an innovative life table analysis for species in which females and males have a different number of stages

The life table data of papaya mealybug, Paracoccus marginatus Williams and Granara de Willink (Hemiptera: Pseudococcidae), on the jatropha, Jatropha integerrima (Euphorbiaceae), were collected using individually- and group-rearing and analyzed by using the age-stage, two-sex life table. Because the male individuals have six stages while the female individuals have only five stages, a new method was developed for a correct description of life stages and life table analysis. In general, the developmental durations of individually-reared insects were significantly longer than those of group-reared insects. Although the mean fecundity (F = 167.84 eggs/female) and the net reproductive rate (R0 = 62.10 offspring) of the individually-reared cohort were significantly higher than those of group-reared cohort (F = 66.5 eggs/female and R0 = 18.62 offspring), there were no significant differences in the population growth rates, i.e., intrinsic rate of increase r and finite rate of increase λ. Because the age variable x is an exponent in the Euler-Lotka equation, the first reproductive age and total preoviposition period are important factors in the determining the value of population growth rates. The life table data were used to simulate the population growth and timing of the control. Our results demonstrated that for group-lived insects like papaya mealybug, life table data collected using group-reared cohort is a better option for simulating pest population growth and management than data from individually-reared cohort.