Studies have shown that the East African mosquito strain, Culex pipiens fatigans, is attracted to a synthetic oviposition attractant pheromone in the laboratory. Chemical analysis has shown that the main volatile component of the apical droplets is (—)-(5R,6R) erythro-6-acetoxy-5-hexadecanolide. In contrast to the lack of response in the Sri Lankan strain of the same mosquito, the East African strain shows remarkable similarity in attraction response to the West African, American and Japanese strains of C. p. fatigans.