Tree frogs serve as a hotel for moth flies

Antagonistic interactions between frogs and insects are generally well-documented. In typical predator–prey interactions, these taxa feed on one another at different life stages. Moreover, insects can function as disease vectors or as parasites of frogs, an example being myiasis-causing flies. However, certain antagonistic interactions between frogs and insects are poorly known, specifically interactions that are mediated by sensory cues such as sound or smell. Here, we report an unusual association between Hyloscirtus lindae (Hylidae) and moth flies (Diptera: Psychodidae, Sycoracinae).

On 26 September 2021, JC observed more than 50 individual moth flies (Sycorax sp) on one male H lindae in a high-elevation Andean cloud forest (around 3000 m above sea level) within Ecuador's Napo province. The male tree frog was actively calling from a Guadua bamboo, at 1.5 m above the ground, under a light rain, close to a small creek. Meanwhile, male and female moth flies interacted with each other on the frog while the frog was calling. This reproductive behavior, known as lekking, has been previously observed in moth flies of the island of Borneo in Southeast Asia, specifically upon frogs of the Bufonidae, Microhylidae, and Megophryidae families. Similarly, in Ecuador, male moth flies are suspected to congregate on frogs to locate female moth flies with which to mate. Sycorax moth flies have been documented forming leks on actively calling male frogs, who advertise their presence to conspecific females through acoustic vocalizations. One possible explanation for how moth flies locate male frogs is through eavesdropping of the male frog advertisement signal. However, no study has tested this behavior to date. It has been previously suggested that moth flies form leks on male frogs because it provides an opportunity for lekking female moth flies to partake of a blood meal after copulating; however, we did not observe feeding on this occasion.