Hello and welcome to FF ! Feeding your frog wild house flies has the risk of them being exposed to chemicals. Your tree frog should take live crickets bought on pet shops with no problems. Crickets should be sized same as distance between frogs eyes and dusted weekly with Calcium 2X and vitamins 1X (Repashy and RepCal are good) on diferent days with skip day in between. Here is an excellent care article with more info on them: Frog Forum - Gray Tree Frog Care and Breeding .