The diel periodicity of pupation and emergence was studied in Culiseta inornata (Williston) under field conditions in the Lower Sonoran Desert of southern California. Floating isolation units were employed for observation of these two phenomena over an 8-day study period. Both male and female pharate pupae exhibited a diel periodicity of pupation. Two daily modes were apparent for this process; the first, of lesser amplitude at around 0400 h, and the second, main peak, near 1600 h daily (sunrise: 0635 h, sunset: 1559 h). Distinct diel periodicity of emergence was evident for both males and females of Cs. inornata, with the peak more pronounced for females. For both sexes, a single combined peak of emergence activity occurred daily at around 1600 h.
The diel periodicity of emergence correlated significantly with fluctuations in water temperature. Other environmental conditions such as solar radiation, cloud cover, windspeed, and air temperature exerted no observable effect on pupation and emergence activity.