Natural populations of these snails are usually found in tropical standing water or freshwater in South America and Africa, but they also reach 30° latitude in subtropical areas. Many species of these red-blooded planorbid snails (Gastropoda: Basommatophora) are able to survive a long time when removed from their freshwater habitat. Of the 34 "Biomphalaria" species, 4 ("Biomphalaria glabrata", "Biomphalaria pfeifferi", "Biomphalaria straminea", and "Biomphalaria tenagophila") have recently expanded their native ranges. They have been introduced to areas where other "Biomphalaria" species are endemic (e.g., Congo and Egypt) or to subtropical zones that have no frost period (Texas, Louisiana, Florida, Hong Kong).