I believe I have 4 live larvae of this species, though two seem like they might not make it. Also 1 aborted mine and a couple of empty ones. I note that in some the mines follow along the decurrent leaf blade into the petiole, where it is too thick and hairy to tell what is going on.

Any suggestions for rearing? Are they likely to pupate in the mines?

These should exit to spin cocoons as with Stigmella spp., and I would rear them the same way. Please press the empty and aborted mines, and if any of the live larvae die you can press those leaves too--with any luck we can get a DNA barcode that will match a known species, even if we don't manage to rear adults.

My impression with the leaf you sent is that the egg was laid well down the petiole, and the larva mine up along one leaf margin, then doubled back, returned to the petiole, and then mined along the other leaf margin. I wasn't able to find the egg because the petiole was curling around itself. Do some of the new mines clearly start in the leaf blade rather than in the petiole?

The one I sent was the one I thought was laid in the margin, then looped around - but I think you got a much better look at it. With respect to the new ones, I saw no eggs - but the lower petiole gets very dirty (the host around here is predominantly on sandy knolls) and is very difficult to wash.

I have searched, but no.
In addition to the ophiomyiids, I have seen some pronounced leaf curling continuously along the margin of one side of the leaf (2 specimens), But there is no evidence of frass, and I am not convinced it is of insect origin (though there is some epidermal separation).

I have also seen 3 small blotch mines with frass, but unoccupied.