Despite researchers having little fondness for them, a large fraction of the world’s biodiversity consists of parasites. Natural populations of organisms are often strongly affected by factors of their environment, most notably the effect of predators. Yet, the most outstanding arms race, produced by millions of years of coevolution, is seen between parasites and their hosts. Bats, the second-most diverse mammal order worldwide, are parasitized by numerous lineages of arthropods; bat flies are the most conspicuous. In turn, bat flies themselves can be parasitized by Laboulbeniales, fungal biotrophs of arthropods. This example of hyperparasitism—a condition where a secondary parasite develops within or on another parasite—of bats, bat flies and fungi, is a severely understudied phenomenon.