Bloodbats are a species of animal briefly encountered ✣ by Agatha, Violetta and Moloch while sheltering on a rafter in Castle Heterodyne. Very little information about them is offered, apart from the fact they take mass flight at periodic intervals and it's a very bad idea to be around when they do so. Their name may offer an indication as to why the latter is true.
According to a footnote in the novel Agatha H. and the Voice of the Castle, their scientific name is Desmodontinae Extremum Sanguine Comedenti, they are indeed blood-drinkers and they were deliberately imported into the Mechanicsburg area from "the Subterranean Kingdom" by The Black Heterodyne.[1] They are preyed on by Venomous Rafter Toads.[2]
It may be further noted that The Red Heterodyne extended his own stay underground due to acquiring a taste for bats, and although not necessarily bloodbats specifically, it could be speculated that this was one of the many points of contention he had with his brother.