Mosquito distribution in the immigration bird-nested area, Pathumthani province, was investigated from August to December in 2006. Mosquitoes were collected by using CO2-baited Centers for Disease Control light traps in which dry ice was used as a source of CO2 to attract mosquitoes. Six traps were operated from 4 p.m. until 7 a.m. on each study day. Four genera, which were Anopheles, Armigeres, Culex, and Mansonia with 14 species of mosquitoes were collected. Culex gelidus (13.94-59.41%) and Culex tritaeniorhynchus (32.87-70.30%) were most collected species in this area for every month. Other two species with moderate distribution in this area were Anopheles barbirostris (0.76-3.30%) and Mansonia uniformis (1.55-11.36%). Polymerase Chain Reactions were performed for testing Wolbachia infection in Cx. gelidus and Cx. tritaeniorhynchus only. Fifty-four percent (15/28 pools) of Cx. gelidus and none (0/20 pools) of Cx. tritaeniorhynchus were positive for Wolbachia infection. Wolbachia infection in other mosquito species collected in this and other areas need to be investigated to understand species and geographic variation of Wolbachia infection in mosquitoes in nature.