Effect of sex ratio on the life history traits of an important invasive species, Spodoptera frugiperda.

The fall armyworm (FAW), Spodoptera frugiperda, is a dangerous migratory pest. Evaluating the effect of sex ratio on the FAW offspring population is particularly important for field control. In this study, five different sex ratio treatments (female/male = 3:1, 2:1, 1:1, 1:2, and 1:3) were conducted to investigate the effects of sex ratio on the life history traits of FAW. The results showed that sex ratio significantly affected lifetime fecundity, developmental duration of the preadult stage, hatch rate, and emergence rate but had no effect on longevity of parental and offspring adults, larval duration, pupation rate, or number of eggs/moth of offspring. The lifetime fecundity and hatch rate of parental adults and the number of adult offspring/moth were the lowest when the sex ratio was 3:1, while the lifetime fecundity and number of adult offspring/moth were the highest and pupation duration was the shortest when the sex ratio was 1:1. The number of eggs/moth of parental adults and total adults in the F1 generation were higher in male-biased groups than in female-biased groups, and male annihilation appears to be a more effective control strategy. These findings have implications for improving laboratory rearing, population forecasting, and control of FAW in the field.