SUMMARY
Quantitative samples of fruit flies communities (Drosophila spp.) were taken with banana baits in the reserves of the Institute Nacional de Pesquisas da Amazônia - (INPA). World wildlife Fund-US Minimum Critical Size of Ecosystems projetc. Data are presented from samples taken in non-isolated reserves (virgin, continuos forest) and in isolated from samples taken in non-isolated reserver (virgin, continuous forest) and in isolated reserve of approximately 1 and 10 ha, as well as the cleared areas surrounding these reserves. The results demonstrate marked differecens between the faunistic composition of the areas continuous forest, were sibling species in the Willistoni group predominate and the cleared areas, where D. latifasciaeformis and D. nebulosa were the most abundant species. In the interior of isolated reserves, the relatives predominance of species found in continuous forest was similar to that measured in the undisturbed sites, with the addition of four species common in opens areas. Of these D. marekotlianawas the only species that was frequent in the interior of the isolates.