Dry-ice trap collection of mosquitoes at urban areas surrounding Tokyo, Japan in 2003 and 2004

Mosquitoes were collected by using dry-ice traps at urban areas surrounding Tokyo, Japan, in 2003 and 2004. Twelve and 18 collection sites were selected beside human houses in 2003 and 2004, respectively, and a battery-operated suction trap with 1kg of dry-ice was operated weekly for 24hr. A total of 6 mosquito species were collected, and among them the Culex pipiens group and Aedes albopictus were the dominant species in the study areas. The average number of collected females /trap/day for Cx. pipiens gr. and Ae. albopictus was 7.4 and 1.8 in 2003, and 9.4 and 2.0 in 2004, respectively. A large variation in the number of the collected mosquitoes was found among the collection sites. Aedes albopictus was collected from May to October, while Cx. pipiens gr. was found from April to December. To distinguish females of Cx. pipiens pallens and autogenous Cx. pipiens pipiens, the ommatidial number of the collected females was examined, and autogenous Cx. pipiens pipiens was found from all the collection sites. Culex pipiens pallens, autogenous Cx. pipiens pipiens and Ae. albopictus were considered to be potential vectors of the West Nile virus at urban areas surrounding Tokyo, Japan.