I put the piece of leaf into my little viewing tin, where I could watch and see what happened next. Later on, I had a better idea, and looked over the tree until I found two more leaves with the sleeping bugs; these leaves I harvested with stems, and put them in water in a small aquarium with a good lid.
These "beetles," like the first two, were also lined up on the central vein of their respective leaves.
I've been watching all week; nothing changed until tonight, when I noticed that one of the tinned bugs had a big hole in the rear abdomen:
Evacuated bug on a drying leaf.
A tiny fly was flitting around in the tin. I checked the aquarium; sure enough, both bugs had holes in more or less the same location. And a tiny fly raced up and down the walls.
And another on a still-fresh leaf.
The flies were very small, very fast. I managed to photograph one:
Black fly on a vintage cats-eye marble.
The other, the one in the tin, I trapped (it took me a while) and dumped in a container where a lame spider was resting; he woke up and caught it in less than a minute.
"Just what the doctor ordered!"
So what has been happening? Were these bugs parasitized by the flies before they settled on the leaves, or afterwards? Or are they a previous stage of the flies themselves? (This doesn't seem possible, but I keep running into "impossible" things.)
Help! I don't even know where to start looking for these. Any and all hints, suggestions, wild ideas are welcome.
*Update: see comments for answers, also the follow-up post, The Case of the Pregnant Mummies.