Since 1936, investigations have been undertaken in an effort to devise a collecting method which can be depended upon to give uniform and accurate information concerning A. quadrimaculatus density. Many sorts of trapping devices have been tested under diversified conditions, including the New Jersey light traps, various combinations of animal baited traps, earth dugouts and box shelters of many sorts.
Our observations indicated that an empty nail keg carefully located on the ground in a shaded situation tends to satisfy the natural requirements of a diurnal resting place and has proved to be a practical means of collecting A. quadrimaculatus. Attempts to improve upon the natural conditions by alterations in the microclimates of the kegs have failed. When both barns and keg shelters were inspected in the same areas for A. quadrimaculatus mosquitoes, both in general showed concurrent increases or decreases in mosquito population. Usually the barns serve as nocturnal feeding grounds and are not comparable to diurnal shelters. Most of the mosquitoes collected from the barns are freshly engorged females; while those collected in the kegs are represented by males and females. The mosquitoes enter the kegs at dawn at the first sign of light, where they rest throughout the day. They leave at dusk and others will not enter the kegs until dawn of the next morning.
For these investigations it is concluded that light traps and baited traps do not give an adequate measurement of A. quadrimaculatus density. It has been established that this species seeks a suitable diurnal shelter at dawn. An empty nail keg tends to provide such a shelter. These keg shelters, when properly located near mosquito breeding places, show promise as a means of defining anopheline densities in localized areas. They have the advantages of uniformity and mobility which, of course, are lacking in conventional collecting stations.
Associate Biologist, Health and Safety Department, Tennessee Valley Authority, Wilson Dam, Alabama.
Read at the Annual Meeting of the American Society of Tropical Medicine at St. Louis, Mo. November, 10–13, 1941.