Sugar feeding and mating promoted the expression of autogeny in Culex tarsalis. In sugar-fed cohorts fed 5, 10, and 20% sucrose solution, the mean number of egg rafts/female, mean number of eggs/raft, mean number of eggs/female, mean number of autogenous follicles/female, and the autogeny rate were all significantly greater than those in sugar-deprived cohorts. There were no significant differences in these parameters among the sugar-fed groups of 5, 10, and 20%. Similarly, magnitudes of the parameters mentioned above in female-male cohorts were significantly higher than those in female-alone cohorts. There was no difference in the hatching rate of the autogenous egg rafts in the cohorts fed on different sucrose solutions and the female-male cohorts, while it was 0 in male-deprived cohorts. There were positive correlations between mean emergence weight and mean number of autogenous eggs/female (r2 = 0.69), mean emergence weight and mean number of autogenous follicles/female (r2 = 0.75), mean wing length and mean number of autogenous eggs/female (r2 = 0.64), and mean wing length and mean number of autogenous follicles/female (r2 = 0.63). The regression analysis of the data indicated that females with emergence weights < 1.92 mg could not oviposit autogenously, and those with emergence weights < 1.89 mg could not develop the ovaries autogenously. Females with wing lengths < 2.89 mm could not oviposit autogenously and those with the wing length of < 2.83 mm could not develop the ovaries autogenously. The coefficient of correlation between emergence weight and autogenous follicles/female was greater than that between emerging weight and autogenous eggs/female. The coefficients of correlation between emergence weight and autogeny were greater than that between wing length and autogeny. Therefore, autogenous follicles/female is a more accurate parameter to describe autogeny expression level than autogenous eggs/female because oviposition is affected by other factors, and emergence weight is a more important factor determining autogeny expression than wing length.