Effects of bush Clearance on Flighting of West African Anophelines

Abstract

1. Two huts were selected which were surrounded by dense bush, which varied in height from 4 to 15 feet. After elimination of this bush within a radius of 140 yards from these huts, the proportion of the population of ♀ A. funestus and ♀ A. gambiae attracted to them was at least 90 per cent. of the proportion which reached them before the bush clearance. This result indicates that bush clearance is not a justifiable measure for reducing Anopheline infestation. Even the male Anophelines entered the cleared area in the same proportion as they did before clearance.2. While bush clearance was in progress there was a temporary sharp reduction in the infestation, and the proportion of the female Anopheline population attracted declined to between one-third and one-quarter of the proportion attracted before clearance. The proportion of males dropped by one-half. At the same time the ♀ Anophelines were apparently much less able to discriminate between quantitative olfactory stimuli. Both effects are attributed to masking by an obscuring odour from the cut and withering bush.3. There was no difference between the numbers of A. melas attracted to a hut screened by a 10 yard thick belt of dense high bush and the numbers attracted to an identical hut in the adjacent clearing 25 yards away.