Abstract
Wing-length frequency of overwintering Culex pipiens pallens from six localities of Japan was not distributed normally because of minority of shorter-winged mosquitoes. From the results of wing-length distribution analysis, the overwintering Cx. p. pallens populations in Japan were considered to be composed of two or three wing-length groups. R-ratio of the wing vein was smaller in the shorter-winged group and larger in the longer-winged group. R-ratio of the population, however, showed normal distribution and the mean R-ratios were within the range of Cx. p. pallens. Parous rate was higher in the shorter-winged mosquitoes. It was concluded from these results that the shorter-winged mosquitoes emerged earlier than the longer-winged group and joined to the majority of the overwintering group. Regressions were observed between each of wing length, R-ratio and body colour and the latitudes where the mosquito populations were sampled. Between wing length and R-ratio, linear regression was significant in each of the populations and also among the six populations; the regression coefficient was much larger among the populations than within the population.
