A complement of one 0.3 m3 red box, CDC miniature light trap baited with dry ice (CO2 light trap) and New Jersey light trap were placed at 4 locations in northern California to evaluate their effectiveness in sampling Aedes melanimon, Anopheles freeborni and Culex tarsalis. The CO2 light traps collected the largest numbers of Cx. tarsalis. Both of the light traps were equally effective for sampling Ae. melanimon. New Jersey light traps were most effective for collecting An. freeborni. The highest proportions of gravid and blood-fed An. freeborni and Cx. tarsalis were collected in red boxes and for Ae. melanimon in New Jersey light traps. Parous rates were highest for female Cx. tarsalis sampled by CO2 light traps, for females An. freeborni sampled by either CO2 light traps or New Jersey light traps and for female Ae. melanimon, sampled by New Jersey light traps. Males and teneral females were more abundant in traps located near breeding sources.