Merriam-Webster Collegiate Dictionary - vampire bat

 noun  Date: 1790 any of several Central and South American bats (Desmodus rotundus, Diaemus youngi, and Diphylla ecaudata of the subfamily Desmodontinae of the family Phyllostomidae) that feed on the blood of birds and mammals and especially domestic animals and that are sometimes vectors of disease and especially of rabies; also any of several other bats (as of the families Megadermatidae and Phyllostomidae) that do not feed on blood but are sometimes reputed to do so