An analysis has been made of the composition of the sylvan mosquito fauna of a well developed virgin tropical rain-forest in which yellow fever appeared in 1951. The results are based on two years of collecting mosquitoes attacking human baits on the ground and in the forest canopy, during the daylight and evening hours. The circumstances under which yellow fever occurred are given, and the climate and microclimate of the rain-forest summarized. It is shown that in true rain-forest the vertical stratification of the sylvan mosquito fauna is much more pronounced than in open deciduous forest. The daily activity cycles of 19 species are illustrated, and an analysis made of the regularity of attack in the case of five species known or suspected as sylvan yellow fever vectors. In addition the annual abundance cycles of 19 species are given.
Present address: The Rockefeller Foundation, 49 West 49th Street, New York, N. Y.