Qualitative and quantitative characteristics adult Culex pipiens fatigans populations according to time, site and place of capture.

The composition of a vector population is largely influenced by the pressures and modifying effects of the environment. Changes in the latter, whether natural or induced (e.g., by insecticides) will be reflected in the former. Thus if the existing characteristics of a vector population are determined, the parameters can subsequently be used to assess the effect of control measures.The effect of environmental conditions on the density and parity of Culex pipiens fatigans in catches in Burma is illustrated by a comparison of results obtained in Kemmendine, which is served by a bucket system for the removal of night-soil, with those from South Okkalapa, which has pit latrines; in the latter area there is a large preponderance of young mosquitos in the monsoon period, in contrast to the situation in Kemmendine.In Kemmendine, the inside-biting catch is reduced by about one-half if an inside-resting catch is made simultaneously. This suggests that C. p. fatigans rests indoors before biting indoors and that an efficient insecticide for inside application would markedly reduce the mosquito population. When a correction is made for the inside-resting catch it is shown that there is little to choose between inside- and outside-biting catches as measures of the activity of C. p. fatigans. The chances of acquiring infection are at least as great out of doors as indoors and this may account for differences in infectivity among different ethnic groups, according to the extent that they sleep out of doors.Differences in parity and in the state of infection of mosquitos according to the type of catch and the time of catching are discussed. Finally, it is noted that, although most male mosquitos are obtained in inside-resting catches, a considerable number, surprisingly, are taken on bait; the reason for this is not yet known.