The Smithsonian Venezuela Project (SVP) conducted extensive surveys of mammals and ectoparasites in the 1960s. The 25 238 individuals and 130 species of bat collected by SVP hosted 36 663 streblid bat flies, representing 116 species of these ectoparasitic dipterans. Roosts of bat species differ in durability and protection, and bat flies separate from the host to pupate in the roost. We predicted higher levels of parasitism and more parasitic associates for bats roosting in more permanent structures (e.g. caves, tunnels) that would facilitate their association with hosts. We also predicted wing development of flies should correlate inversely with roost duration, restricting flightless forms to bats in permanent roosts. Ranking roosting structures by durability and protection, we sought correlations among bat species in prevalence, mean intensity and number of associated fly species. All three measures of parasitism were positively and significantly related to roosting habits: bats roosting in more permanent, enclosed structures were more likely to be infested, to carry heavier parasite loads, and to harbour more species of ectoparasitic flies. However, roosting habits were not correlated with the average wing development of bat flies. Although other factors affect parasitism rates in bats, the study provides a compelling example of both ecological and evolutionary responses of parasites to features of the host's environment.

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An extensive survey of the ectoparasites infesting bats in Paraguay provides information regarding the taxonomy and host distribution of streblid bat flies at a geographic interface between subtropical and temperate habitats. Five families of bats representing 45 species, including Molossidae (5 genera and 15 species), Natalidae (1 genus and 1 species), Phyllostomidae (11 genera and 15 species), Noctilionidae (1 genus and 2 species), and Vespertilionidae (4 genera and 12 species) were collected from 24 localities across Paraguay and sampled for ectoparasites. In total, 2,467 bat flies were collected, representing 11 genera and 31 nominal species of Streblidae, of which 6 genera and 24 species are new records for Paraguay. No streblids were collected from vespertilionid bats; 23 species infested phyllostomids, 6 species noctilionids, 1 species a natalid, and 1 species molossids. Streblid bat flies were highly specific to certain host groups and individual host species, and their geographic distributions closely followed those of their host bats. Of 31 streblid species surveyed, 27 were monoxenous (i.e., associated with a single host species), and 4 were stenoxenous (i.e., associated with a group of phylogenetically related hosts). The number of streblid species is greatly reduced in the Chaco region west of the Paraguay River, largely because of the lack of phyllostomid host bats. Streblid flies are obligate, blood-feeding ectoparasites of bats. In temperate North America, they primarily infest vespertilionid bats (Wenzel, 1970; Guerrero, 1994), and a few species over winter on hibernating bats (Zeve, 1958; Reisen et al., 1976). However, in Central and South America, the species richness of these flies is increased, primarily in association with phyl lostomid bats (Wenzel, 1970). The most important previous studies regarding the taxonomy and distribution of neotropical Streblidae were based on faunal surveys in Panama (Wenzel et al., 1966) and Venezuela (Wenzel, 1976). During those studies, 10 new genera and 94 new species were described, and the taxonomic foundation of New World Streblidae was estab lished. However, very little is known about the distribution and host associations of streblid flies infesting bats in the subtrop ical and temperate regions of South America. From 1991 to 1997, bats of the Yungas Forests in Argentina were surveyed for ectoparasites (Autino et al., 1999). Although 37 bat species are known from this region, which includes sites in the Argen tine provinces of Jujuy, Salta, Tucuman, and Catamarca, only 7 species of streblids were reported (Autino et al., 1999). In southern Brazil, 23 species are known from the state of Paran? (Graciolli and de Carvalho, 2001) and 11 species from the state of Rio Grande do Sul (Graciolli and Rui, 2001). An extensive, 5-yr survey of ectoparasites infesting bats in Paraguay provided the opportunity to increase our understanding about the distri bution of streblid bat flies across hosts and habitats at the in terface of subtropical and temperate zones. Parag...

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