The cocoon got much more opaque after the first day.
Now I can’t see the caterpillar at all, and the cocoon has turned brown.

One other caterpillar has made a cocoon – sticking both to one of the lilac branches and to the water jar. I’m not sure how to get the jar out to clean it. Hopefully all the caterpillars will make their cocoons soon, and I can get in to reorganize and clean out the cage.