FRESHWATER LEECHES (ANNELIDA: HIRUNDINEA)
Elliott & Mann (1979) list 16 British species. ten of these are recorded in Cornwall, all being nationally common (A. Brown, pers. comm.). The blood-sucking leech Hirudo medicinalis Linnaeus attains 85mm at rest and does not occur in Cornwall. The largest Cornish species, the Horse Leech Haemopis sanguisuga (Linnaeus), grows up to 60mm long and swallows smaller invertebrates whole; it also takes tadpoles and other very small or wounded vertebrates as well as carrion. Others suck the blood of birds, fish and/or amphibians or the body fluids of invertebrates. One of the commonest species Erpobdella octoculata (Linnaeus) is a carnivore, not a parasite.