Raspberries are being eaten by bluebottle flies

I often hear of raspberries and blackberries being eaten or tapped by insects such as wasps and flies even when they are just beginning to ripen. I have bird netting over my berries. The meshing is dense enough that keeps the insects at a distance from the fruit. Unlike birds, the insects usually do not fly into the inside of the net from below. If they unfortunately manage to get in, you would need to tie up the bottom part of the net fairly tightly, as you would do to counteract birds.