Two orhthopteran insects having multiple mating system were studied on the view points of the mate choice and the benefit of mating for the female with special reference to sperm competition.
In Atractomorpha lata, the effects of body size and age on the mating frequency were measured. Middle size of females mate more frequently than smaller or larger sizes. Female body size was correlated with emerging season, namely the latter date of emergence, the smaller females appeared. Therefore, in the females emerging latter season (in September), a size dependent increase of mating frequency was observed. Also, the positive correlations were observed between age and mating frequency in both female and male.
The females Truljalia hibinonis feed a sticky material, which secreted from male metanotal gland. The effect of metanotal secretion feeding on female egg production was examined with the relation to the multiple mating system. The fecundity of females offered the secretion multiply was significantly lower than that of females of single mating. Moreover, there was a negative correlation between the consuming level of metanotal secretion and mature eggs in ovary at 40 days old. The adaptive significance of this phenomenon is a quite interesting problem to solve in future.