Papaya fruit fly... You can try bagging them. They start "stinging" them when very young, but I found that the rind is either too thick or hard and the larvae do not "take" But, once they get to about 2" long, if I do not bag, they get them.
Even then with my mesh bags they can deposit the eggs. The only thing I can do is hope I get them to maturity not injected. Once I pick, I ALWAYS refrigerate them just in case there is larvae and they die. Throwing them in the garbage before refrigerating will keep the cycle going.
PS, I don't bag all of the fruit, I leave some to be "easy targets" for egg deposits and as they mature, I know they're likely infected, refrigerate, and throw away.
Oh, I also inspect the fruits a few times a day and "shoot" them with an open rubber band and kill any fruit flies on the trees.