Nail snail, _ conch family nail snail genus mollusks. Nail snail has female and male points, amphibious, by the shell and soft body of the two parts, the soft body part of the front for the head, neck, feet and coat membrane, the back is the viscera, is the main intermediate host of Schistosoma japonicum. Its larvae mostly like to live in the water, adults generally like to live in the grass above the water line in the humid zone. Mainly distributed in eastern Asia and Southeast Asia.