My gut feeling is that they eat some insects opportunistically wherever they go. There are only few studies on this, and even less using molecular tools.
Some brazilian frugivorous bat species, such as Rhinophylla spp., Carollia spp., Artibeus spp., Platyrrhinus spp. and Uroderma spp., are know to complement their diets with insects (not only Lepidopterans). Some megachiropteras were also reported to ingest different sources of animal protein.
This paper may be helpful: Dietary strategies of Old World Fruit Bats (Megachiroptera, Pteropodidae): how do they obtain sufficient protein?