|What lived inside this? About 2 inches across.|
I broke a few off. They were all hollow and dry, as thin and fragile as eggshells. There was no sign of their previous occupants.
|This one seems to incorporate a dried leaf.|
I looked up aspen galls, and found leaf galls;, small blobs that grow right at the base of the leaves and twig galls; small, smooth balls lined up along a twig, but nothing like these.
Most of the galls had several holes that looked more like chickadee predation than insect exit holes. I have watched chickadees with thimbleberry galls in the winter, pounding away at them until they crack open. Somehow they know there's good meat inside that hard casing; maybe the larva inside moves around, makes some sound that we can't hear, but the chickadee can.