Abstract
1. A seasonal study was carried out on the mosquito population breeding in rock pools in the river bed of Nagatoro, Saitama Prefecture, during the period from January 1966 to February 1968, with emphasis on the bionomics of the little known mosquito species Aedes hatorii Yamada, 1921. 2. As the results of 50 times of collections made during the period, a total of 53, 148 larvae belonging to 10 species in 3 genera were identified. Among them, Aedes hatorii was the predominant and constituted 84.7% of the larvae and pupae collected, while Aedes japonicus was the next common species with 9.7% of the total collections. 3. The population density of Aedes hatorii was the highest during the summer season from July to September, while Aedes japonicus was almost absent in the summer and was found to be breeding most abundantly in early spring. 4. The two species were shown to survive the winter in egg and or mature larval stages. 5. The principal breeding places of Aedes japonicus were rock pools in shade, while Aedes hatorii was found almost in every pool including those in open areas.
