(Uploaded by Plazi for the Bat Literature Project) Although closely related host species are similarly susceptible to infestations of parasites, even small differences in their morphology, feeding behaviour or population history may affect parasitic infestation. In the present study we analyse the abundance of two species of nycteribiid flies (Diptera, Nycteribiidae) and one wing mite (Mesostigmata: Spinturnicidae) infesting populations of Miniopterus schreibersii and M. pallidius, which comprise a cryptic species complex of Miniopterus species in Asia Minor. We focus on the putative contact zone between these two taxa in Central Anatolia. We conducted our study in seven caves with large (≥ 1,000 individuals) maternity aggregations: three housing Anatolian M. schreibersii, one housing Levantine M. schreibersii, and three housing Anatolian M. pallidus. Sex-biased parasitism was found only twice: female-biased in Spinturnix psi on M. pallidus, and male-biased in Nycteribia schmidlii on M. schreibersii. Differences in the flies' abundance between Anatolian M. schreibersii and M. pallidius were found only in N. schmidlii (for female host), but not for Penicilidia dufourii. There was a significant difference in the wing mite abundance, both between hosts and sexes. Unexpectedly, we observed a large difference in the load and type of parasites between M. schreibersii from Levant (separated from other M. schreibersii colonies by a few colonies of M. pallidus) and the rest of M. schreibersii. In Levant, the wing mites did not infest bats. Instead, they carried almost threefold larger load of the flies than in other bent-wing bat colonies. It is possible that the decline of wing mites is associated with increasing quantities of flies. One hypothesis regarding the absence of S. psi in the Levant colony, is that it is correlated with a significant decrease in the size of the bat's population in the past (as indicated by both mtDNA and microsatellite studies) and their disconnection from the continuous range of other M. schreibersii. We did not find any correlation between parasite load and health status of the host.