Twenty-three mosquito species were collected feeding on floral nectar at 3 study sites. Each of the 9 most abundant species exhibited specific peak feeding periods with respect to twilight. Twilight times were expressed in crep-units. Aedes stimulans peak feeding occurred around 0.5 creps or mid-civil twilight. Aedes canadensis, Aedes communis, Aedes sticticus, Aedes vexans, Coquillettidia perturbans , and Culex restuans exhibited peak feeding activity around 1.0 to 1.5 creps or early nautical twilight, while Anopheles earlei and Anopheles walkeri fed later in nautical twilight. These 2 anophelines are known to be more active late at night, especially in search of a blood meal. Aedes stimulans fed on nectar for some time before sunset; this species is known for its aggressive daytime feeding activities, suggesting that nectar-feeding and blood-feeding activities with respect to photoperiod may be similar. Males and females of some species, such as C. perturbans , exhibited different peak feeding times, while for other species, such as A. vexans, A. canadensis, C. restuans , and A. earlei , both sexes fed at almost identical times, the correlation coefficient (r) of feeding being generally greater than 0.900. Microclimatic factors greatly influenced feeding, reducing it when they existed as extremes. Wind above 10 km/hr acted as an inhibitor to feeding, as did temperature below 10.0/C and relative humidity below 48%. The data suggest that the time of peak feeding activity is controlled by a circadian or photoperiodic rhythm, but that the level of illumination affects the initiation, cessation, and duration of feeding on a given night.