Leeches

More than a dozen species of leeches, primarily from the family Hirudinidae, are used for hirudotherapy.

An excerpt from the article 20 facts about Leeches
The most commonly used species are Hirudo verbana - the Asian-Southern European, Hirudo trctina - the African species, Hirudo orientalis - the Asian species and Hirudo medicinalis - the medicinal leech, which is under strict species protection in many countries.