I found one other grouping of exuviae in the area where I found the one above. I’ve never seen anything like this locally. I believe these are from lepidopterans. There is a slight layer of silk on the bark. Up close, I saw some cast off head capsules. Look closely above, and you’ll notice a leg that must have broken off while struggling free.
I know some caterpillars are gregarious as early instars, but I thought they generally went their separate ways as final instars. I thought this was interesting evidence that in at least one species, they pupate and perhaps eclose together.