Acoustic preferences and localization performance of blood-sucking flies (Corethrella Coquillett) to túngara frog calls

Mating signals that increase attractiveness of males to females can also increase conspicuousness of the signaler to predators and parasites. We investigated the acoustic preference of species of blood-sucking flies of the genus Corethrella (Diptera: Corethrellidae), which eavesdrop on the sexual advertisement signals of túngara frogs (Physalaemus pustulosus). Male frogs of this species facultatively produce 2 types of mating calls: simple (whines alone) and complex (whines and chucks). We tested the acoustic preference of the flies and their ability to locate their host when the frogs produce simple or complex calls. The flies exhibited phonotaxis to both types of calls but were preferentially attracted to complex calls. We show that acoustic information alone is sufficient for the flies' accurate localization of calling frogs. Complex calls, however, were not approached at closer distance or with decreased landing error (i.e., proportion of landings outside the target) than simple calls, suggesting that call structure does not influence localization performance. Female túngara frogs and frog-eating bats (Trachops cirrhosus) also prefer complex to simple túngara frog calls. Thus, intended and unintended receivers with different ear morphologies exhibit the same preference for a specific túngara frog call type. This result is discussed in the context of the evolution of call attractiveness in a communication network.