ABSTRACT
In this work, bioassays were carried out in laboratory conditions (average temperature 26 ñ 2ºC) to test ten strains of Bacillus sphaericus, isolated from Brazilian soils third instar larvae from anopheline species recorded as malaria vectors in Amazonian - Anopheles nuneztovari and An. darlingi. With the former mosquito, three strains - S 2', S 20 and S 46 showed relative activity, in 24 and 48 hr exposure to the B. spahericus strains. With the latter only the S 20 were effective in the 48 hr reading. The studied strains that showed the most adequate response in the Amazonian region were S 2 and S 20 showing broader and more efficient results. Therefore, S2 was the most effective when the 24 and 48 hr reading were considered, because it showed the greatest relative activity values.