Total protein, lipid, and glycogen of Aedes vexans (Meigen) were related linearly to body size at eclosion. Starvation after emergence led to the determination of minimal irreducible amounts of protein, lipid, and glycogen and the availability of the teneral reserves, whereas access to sucrose revealed the potential for reserve synthesis. Glycogenesis and lipogenesis increased reserves ≈10-fold the teneral value within 1 and 2 wk after emergence, respectively. Carbohydrate feeding was an essential behavior before blood feeding and oogenesis commenced. Female flight was tested on a flight mill. Maximal flights of 10–17 km in a single night occurred at 2 wk posteclosion and paralleled maximal reserve syntheses. Comparisons of our laboratory data to host-seeking mosquitoes in the field confirmed our data. The vast majority of maternal lipid was transferred to the yolk when a blood meal was taken, but only a quarter of the blood protein was recovered from mature ovaries. Maternal glycogen was used mainly for flight. Fecundity varied between 20 and 120 eggs per female and was determined largely by body size and blood meal volume. At 27°C, maximal egg numbers were produced, but at 22 and 17°C the caloric yolk content was greater. Females from the southern United States were smaller than females from northern areas. However, southern females had similar fecundity as northern females, and their flight performances were similar. Differences in the reproductive physiology between this species and Ae. aegypti were discussed.