抄録
One year observation on the fluctuation of population density of Culex pipiens pallens was carried out in a large cave and in the chicken houses outside of the cave located in the vicinity of Tokyo, from Feburuary of 1963 to Feburuary of 1964. Physiological age was also determined with each collected specimens in accordance with Detinova's method and seasonal changes of age composition of the population were observed. The data on the density combined with those on age composition facilitated the dynamic analysis of natural population of mosquitoes. Five phases were distinguished concerning to activity of mosquito population on the basis of changes in density and age composition; that is, hibernating phase in winter, reactivated phase in the early spring, first generation in spring, proliferating phase in summer, and pre-hibernating phases in autumn. The parous rate of population which is hibernating in the cave was observed constantly at the level of around six or seven per centage. Although all of the parous mosquitoes of hibernating population were found to have only one relic at ovariolar pedicles, the fact indicated that at least a part of hibernating mosquitoes did take a blood meal before entering into hibernation. This would be of interest pertaining to possibility of overwintering of some arthropod-born viruses by adult females of hibernating mosquitoes. The temporal decrease of population density was observed to take place in the midst of summer season. The slight aging tendency which was concurrently noticed in the age composition of adult population of this season suggests that decrease of number of adults could be resulted from decrease of pipiens larvae by their natural enemy, i. g. the larvae of Culex vorax which is well known to breed in breeding places of pipiens larvae in that season. The developing stage of follicles in ovaries were found all remaining at Christophers's I stage in mosquitoes which were hibernating in the cave, however, the most parts of mosquitoes in active seasons were observed to have the follicles at II or III stage. As the latter specimens of mosquito were collected inside of the chicken houses at around three o'clock in the afternoon, and the majority of them were shown to have blood clot in stomach, it may be natural that the follicles had developed to some extent by that time after engorgement. However as it was reported in the previous paper of this series, the period required for the follicles to develop up to II or III stage would be about 24 hours at 25℃, a fact suggested that mosquitoes remained for a considerable period in chicken houses after taking a blood meal.
