Effect of age at first mating on primary sex-ratio of the two-spotted spider mite

This paper determines the influence of initial age at mating on the primary sex-ratio of the two-spotted spider miteTetranychus urticae Koch. The specific question asked is whether females that mate at ages beyond ecdysis, or are inseminated at ecdysis by virgin males of set ages, have daughter productions different from control females mated at ecdysis by randomly aged males.Age of initial female mating did not effect survival. Females mated at ecdysis produced more daughters than those mated at age 5 or 10 days. However, daughter production was equal for all female treatments in the post-mating period. All treatments stopped producing daughters at approximately the same age, regardless of when mated. Son production was lowest for females mated at ecdysis. However, son production by females mated when 5 or 10 days old was lower than that of females mated at ecdysis.Male age at mating did not effect female survival. Females exposed to virgin males either 1 or 7 days old produced more daughters than those exposed to males either 11 or 20 days of age. However, a substantial proportion of females in these latter cohorts were not mated. If only mated females are considered, daughter production is the same between all cohorts.Delayed age at first mating influenced sex-ratio only via the females, specifically by changes in daughter production (as opposed to changes in survivorship). Daughters that would have been produced between ecdysis and mating were never recovered by females that mated at ages beyond ecdysis. Thus, these daughters were lost from a sex-ratio viewpoint. Initial age of male mating did not change sex-ratio.