Leeches are annelids comprising the subclass Hirudinea. There are freshwater, terrestrial and marine leeches. Like their near relatives, the Oligochaeta, they share the presence of a clitellum. Like earthworms, leeches are hermaphrodites. The medicinal leech, Hirudo medicinalis, which is native to Europe, and its congeners have been used for clinical bloodletting for thousands of years.All leech species are carnivorous. Some are predatory, feeding on a variety of invertebrates such as worms,