Seasonal trends in reproductive performance and size were examined among female Mansonia dyari. The incidence of parity ranged between 6.9 and 58.1% and averaged 22.5% during an 8-month interval, with 4 peaks in parous rate believed to follow periods of emergence. Parous rates were positively correlated with wing lengths, indicating size-dependent survivorship. Wing lengths were highest in the winter and early spring, decreased to a minimum at the end of summer, and increased in the autumn, showing negative correlations with ambient temperatures recorded prior to adult capture. Female biomasses and fecundities were positively correlated with wing lengths, and their mean values varied significantly among sample dates. Egg development in Ma. dyari was completed by 5.4 days post blood meal at 26 degrees C and 7.6 days at 20 degrees C. No evidence for autogeny was observed.