We studied the ectoparasitic bat flies of three phyllostomid vampire bat species. Bats were collected monthly from April 2004-March 2005 True ectoparasites spend most of their adult lives, or all developmental phases, on the bodies of their hosts or in their hosts' shelters (Marshall 1982). Streblidae (Diptera: Hippoboscoidea) are obligate ectoparasites of bats (Dick & Patterson 2008) and, consequently, are found primarily in tropical areas with relatively few species in the subtropical and warm temperate zones .Knowledge of bat ectoparasites has provided important information on the host's biology, systematics and phylogeny (Fritz 1983) and is essential for better understanding the ecology of bats and bat behaviour in shelters. This knowledge has also explained aspects of larviposition and infestation by ectoparasites and the epidemiology of pathogen transmission in bats (Komeno & Linhares 1999).The host's roosting habits are important factors in the bat-ectoparasite system (ter Hofstede et al. 2004, Patterson et al. 2007, Seneviratne et al. 2009). The variability in bat roosting preferences and ectoparasite fauna provides significant insights relating to parasite ecology and specificity (ter Hofstede et al. 2004). Host specificity is typical for parasite-host associations and is often even higher in obligate or permanent parasite associa- tions (Dick et al. 2009). Ectoparasites can be classified as heteroxenous when they can infest many species in many genera, monoxenous when they are found on only one host species, stenoxenous when they are found on host species of the same genus and oligoxenous when they are found regularly on hosts of different genera (ter Hofstede et al. 2004).The Brazilian savannah, also known as the cerrado, covers approximately two million km 2 of Central Brazil and is considered one of the richest and most threatened biodiversity reservoirs in the world (Mittermeier et al. 2005). This region is responsible for most Brazilian soy and corn production and ranching in this region produces almost 40 million heads of cattle per year (Aguiar et al. 2008). Bats account for nearly 50% of the total mammalian fauna of the cerrado biome (Aguiar & Machado 2010). This generates a great deal of concern due to their association with rabies, though most rabies cases are caused by just one vampire species, Desmodus rotundus (Gonçalves et al. 2002). Of the vampire bat species, D. rotundus is the most common and widespread species in Central and South America. Their primary food source is mammalian blood, but they also feed on avian blood. The two other vampire bat species, Diaemus youngi and Diphylla ecaudata, are rare and feed mainly on avian blood (Aguiar et al. 2006).There are few studies on bat ectoparasites and their relationship with their hosts in Brazil (Gettinger & Gribel 1989, Komeno & Linhares 1999 Graciolli et al. 2008). The purpose of this study was to investigate the degree of host specificity of the bat flies on vampire bat species in the cerrado of Central Brazil. Previous studies of ect...