While recently reviewing my shots of this fly in the family Micropezidae, I was surprised to find that I unknowingly got a shot of her laying an egg. Here’s another shot for comparison, where she has concealed her ovipositor beneath her abdomen.
Here’s a crop from the first photo, showing the ovipositor and the egg.
Everything I’ve read indicates that most larvae develop in decomposing matter, so it seems strange she would be placing an egg on a leaf surface. Perhaps this is  just a method of random distribution, and the egg just falls where it may on the ground below.