The geographical distribution of Biomphalaria tenagophila (d'Orbigny, 1835) and B. occidentalis Paraense, 1981 in S. Paulo State, Brazil, is described. The first species being the most important intermediate host of Schistosoma mansoni Sambon, 1907. The second species is unsusceptible to transmission. The two species inhabit the limnic environments of great areas of S. Paulo, occasionally in simpatria. The 3,160 samples of mollusks collected between September 1981 and March 1986 were examined. B. tenagophila were identified in 1,062 of these samples from 203 municipalities and B. occidentalis in 255 samples from 97 municipalities. Biogeographical circunstances related to the distribution of the planorbids species are commented on.
Biomphalaria tenagophila; Biomphalaria occidentalis; Schistosomiasis; Ecology, vectors
