I was surprised to see we have no larval images of this species. Adult imported willow leaf beetles were all around this tree, and typical skeletonizing leaf damage obvious too, so I trust this ID is correct - please let me know if you think otherwise.

This was the largest larva I found - close to pupation I would guess.

Another interesting thing was that after I'd been bothering it with my attention for a while, this larva started exuding clear fluid from the projections along both sides of its back - some kind of chemical defense? Unfortunately I did not get a clear image of the droplets.