Hipposideros larvatus of Thailand are parasitized by two new Haemosporidia : a) Nycteria brucechwatti n. sp. can be differentiated from all other Nycteria species by the schizonts which are the largest in the genus and by the absence of accessory chromatin dots in the gametocytes; Biguetiella minuta n. g. n. sp. has very small intra-hepatocytic schizonts (less than 15 micron) and gametocytes of the "falciparum" type. These two species are considered as vicariant forms of parasites of Miniopterus, namely Polychromophilus and Bioccala. The subgenus Bioccala is raised to genus status and problems related to the study of polyparasitic infections of the same host are discussed.