Abstract
Culex tritaeniorhynchus Giles was collected by light traps through the night in cowsheds and pigpens. There was a linear relation between the number of mosquitoes trapped in the outside of a cowshed and the number of mosquitoes in the cowshed (Fig.1). The blood feeding rates decreased depending on the number of mosquitoes per one cow or swine. (Fig.2, 3 and 4). Percent ratios of females with a trace amount of blood meal among entire blood-fed populations increased in accordance with the increase of population densities (Table 1). This suggests that the interference among individual mosquito has an important role when mosquitoes exist abundantly. In every collections, the blood feeding rates of both nulliparous and parous females decreased depending on the number of mosquitoes. But when the number of mosquitoes was over 5, 000, the blood feeding rates of parous females. (Fig.5). When the number of mosquitoes was over 15, 000, the estimated number of parous females began to decrease in a cowshed (Fig.7), but in a paddy fiield, the estimated number of parous females collected by a dryice light trap did not decrease even when the number of mosquitoes was 78, 152 (Table 2). An estimation was thus made that unlliparous females may disperse if the number of mosquitoes was over 5, 000, and parous females may also disperse when the number of mosquitoes increased over 15, 000.
