Hosts-parasites associations, including infestation rates, between ectoparasitic bat flies of the family Streblidae and bats of the family Phyllostomidae were studied in Atlantic Forest habitats in southern Brazil. For the more abundant phyllostomid bats, the prevalence and mean intensity of fly infestation were determined during the different seasons of the year and in relation to the sex and age of their hosts. From four species of bats (Anoura caudifera (E. Geoffroy, 1818), Artibeus fimbriatus Gray, 1838, Artibeus lituratus (Olfers, 1818) and Sturnira lilium E. Geoffroy, 1810), were collected 118 specimens of bat flies belonging to seven species (Anastrebla caudiferae Wenzel, 1976, Megistopoda aranea (Coquillett, 1899), Megistopoda proxima (Seguy, 1926), Metelasmus pseudopterus Coquillett, 1907, Paratrichobius longicrus (Miranda Ribeiro, 1907), Trichobius phyllostomae Kessel, 1925 and Trichobius tiptoni Wenzel, 1976). Low infestation rates were found in A lituratus, A fimbriatus and S. lilium and there were a tendency for the bats to be more parasited in summer and autumn, probably related to the seasonal temperatures in the region studied because such temperatures affect the reproductive and mortality rates of the ectoparasites. For A lituratus, the age or sex of the host did not affect the infestation rates by P. longicrus. Although the age or sex of S. lilium did not, in general, affect the rate of infestation by M. proxima, juvenile S. lilium appeared to be more frequently parasitized by M. proxima than did adult bats. The data indicate that there are no behavioral differences linked to the age and sex of the species of phyllostomid bats studied which favor or disfavor infestation by Streblidae.
