We had a survey on the nature and the propagation of mosquitoes principally of Culex tritaeniorhynchus at the reclaimed land of Fukuda at Kojima District in Kurashiki City in Okayama Prefecture (1967). The survey was made again from April 21 to November 9 in 1970 with the same methods as in 1967. Mosquitoes were collected with the dry ice-trap and the light-trap for two and a half hours starting at 30 minutes before sunset. These results were compared with those in 1967.
1. In 1970 the numbers of Culex tritaeniorhynchus and Anopheles sinensis were both very smaller than those in 1967 (about one tenth). Culex modestus showed a large increase comparing to the number in 1967.
2. The reason of these phenomena was that pigsties which were about 1 km away from the mosquito collecting spot were removed in 1969, and Culex tritaeniorhynchus and Anopheles sinensis lost the principal source of blood meal.
3. 1 and 2. indicate that in this area Culex tritaeniorhynchus and Anopheles sinensis fed on blood of the pigs and kept the activity sphere of about 1 km.
4. Aedes dorsalis hatches with raining and the appearance of the adult reaches its peak 15 to 20 days after hatching. The eggs can hatch even more than 2 months later since being laid.
