Most of the species of Leiognathus are parasitic on small mammals (bats, rodents, etc.), others occur on birds and a few also on reptiles. A number of the species of this genus have been described under the name Liponyssus, butpersonally I do not think that Liponyssus setosus, Kolenati (the type and first described species of the genus Liponyssus) falls into the same natural genus as the species described by recent authors under that generic name or under the name Leiognathus. On the other hand, Kolenati's genera Ischoronyssus, Macronyssus, Lepronyssus, Steatonyssus and Pimelonyssus certainly seem to me to be congeneric with Leiognathus, Cn., and ultimately one of these names will have to replace Canestrini's.