The seasonal chronology of eggs of Culex halifaxii, Cx. fuscanus and their cohabitant Cx. quinquefasciatus were observed from March 1984 to early May 1985 in Okinawa prefecture, Japan. In Okinawajima, egg rafts of Cx. halifaxii and Cx. quinquefasciatus were found throughout the year. The greatest peak in eggs of Cx. halifaxii were observed in early June. The egg rafts of Cx. fuscanus were first collected on June 15, with the greatest peak of oviposition in early November. The egg raft of Cx. fuscanus was larger and both the maximum and mean numbers of eggs per raft were approximately two times greater than those of Cx. halifaxii.