Though I think the new images (https://bugguide.net/node/view/1567064/bgimage) from this year (and the same tree!) are superior to this failed mine and dead larva.



By the way, the larvae let their mines yesterday and are forming their cute Lyonetiid pupation shelters. I'll try to take a picture today.

I kept them mainly because of the view of the eggs; also this is the only shot of a larva out of a mine, though I agree that your new one of the larva inside a mine is much better.

I think I'll take a ladder to the tree, to look for others!
But the number of fungal necrotic blotches, as well as a variety of window feeders, makes such a search especially challenging... And the tree is beginning to drop leaves due to an extended dry spell.

Oh, and note that although this pose is somewhat lifelike, the larva is quite shriveled. Probably was a bit plumper when alive.

this (scroll down a few pages for egg & larva descriptions). The eggs seem to match; the larvae do not have that black thoracic shield that yours has, but maybe that is a feature of the first instar that wasn't observed. Assuming you haven't discovered something entirely new, P. albella seems to be the only possible fit among the known Populus miners. Zeugophora mines are similar, but the eggs are inserted in pits chewed in the lower epidermis.

Sounds like a successful P. albella mine should be very easy to spot, based on the description in the paper. It would not be surprising that hosts stage a vigorous chemical attack against something so devastating.
The eggs sound right.