The comparative effectiveness of NJ light traps, CO2-baited traps, walk-in red boxes, high-intensity light traps and gravid traps for sampling adult Culex mosquitoes for arbovirus surveillance was compared at rural dairy and residential urban habitats near Chino, California. Culex quinquefasciatus was the most abundant of the 3 species present comprising 94.9% of the 23,159 mosquitoes collected, followed by Cx. peus (4.2%) and Cx. tarsalis (0.9%). Female mosquitoes of all species were most abundant in CO2-baited traps at both urban and rural environments. Males were collected most effectively by walk-in red boxes in rural, but not urban, environments. More parous females were collected by CO2-baited traps at urban than rural habitats; however, 70-79% of all females were nulliparous and had never blood fed. These data point out the potential insensitivity of the current sampling methodology in monitoring mosquito arbovirus infection rates.