名古屋地方における蚊族個体群の発生動態 : III. アカイエカ幼虫個体群と成虫個体群とにおける発生動態の関連性

Abstract

An ecological study was made on the larval and imaginal populations of the house mosquito, Culex pipiens pallens Coquillett, in Nagoya City during a period April to November, 1969. The purpose of this report is to elucidate relationship between larval and imaginal population dynamics in natural habitat from the view points of seasonal change of larval population size, larval age structure, imaginal population size and parous rate of adult females. 1) The number of larvae and pupae in a fertilizer pit was estimated by the removal method (Fig. 2), and totalled 11,962 during the study period. Most of them (ca. 98%) were Culex pipiens pallens and the rest were C. tritaeniorhynchus, C. vorax, Anopheles sinensis and Aedes togoi (Table 1). In the vicinity of the fertilizer pit, a total of 123 adult mosquitoes were captured by a light trap during the same period. They consisted of 61% C. tritaeniorhynchus, 38% C. pipiens pallens and about 1% An. sinensis (Table 2). 2) The larval population of C. pipiens pallens occurred from late April to early November, and the population size reached its peaks during late May to early June and in early October (Table 1). Larval age structure was analyzed consecutively and, on the basis of the precursory abundance of the older larvae and pupae, adult emergence at population level was considered to occur about six times. Of these, number of newly emerged adults was estimated to be the largest at the second emergence period (late May-early June) and the next largest at the fifth emergence (late September-early October)(Fig. 3). 3) On the other hand, imaginal population of the species observed by a light trap occurred from early April to early November, and the population size reached its peak in July, after the first peak of productivity of adults observed in the larval population. The second peak of productivity in autumn, however, was not followed by the prominent peak in adult population size (Fig. 3). Parous rate of adult females rose remarkably in early May and during late September to early October, and number of egg rafts in the fertilizer pit increased in parallel with the rises of the parous rate (Fig. 3). 4) Life cycle of the house mosquito in spring in this district was summarized as follows : (a) Completion of overwintering of the adults around March to mid April, (b) appearance of the first larval population in late April, (c) appearance of imaginal population in early May.