The carnivorous ant Paratrechina longicornis was found to be an active predator against estivating snails of the genus Biomphalaria. As soon as the snails are left in the dry land by the receding waters during the dry season, they are attacked and quickly eaten by the ants. Only the snails buried in the claysh mud or those which have their shell openings obturated by lumps of hardened clay are apt to escape predation and return to activity when the forthcoming wet season brings water to the dryed-up breeding sites. Obviously other species of carnivourous ants may play the same ecological role.