Abstract
Some analyses were made on the overwintering populations of the house mosquito, Culex pipiens pallens, collected during the period from October 1969 to March 1970,and on the field populations sampled in a hen house and a pigsty from May to November 1970. 1) Wing length distributions of parous females were compared with those of all the overwintering females. The wing length of the parous females distributed in shorter ranges of the overwintering population, and a general trend was observed that the shorter the wing, the higher the parous rate (Fig. 1). This seemed likely that many of the female mosquitoes belonging to the overwintering short-winged group joined to the long-winged group after blood feeding and oviposition in the prevalent season. 2) Parous rate of the population decreased from about 8% at the beginning to 4% at the end of overwintering period (Fig. 2). This seemed to imply that mortality of the parous females was slightly higher than that of the nulliparous ones in the overwintering population. 3) In early summer, average wing length of the field populations collected in a hen house and a pigsty, was at a level of the overwintering population, and decreased to the minimum at August. It remained at the average level of the overwintering short-winged group from around September to early October, but in early November appeared a small number of individuals with average length near to that of long-winged group (Fig. 3). Both in the hen house and in the pigsty populations, the parous rate increased remarkably in autumn and reached to the maximum in early October, when the average wing length remained at the level of the overwintering short-winged group (Fig. 3).
