So after I made that post I did some reading on "bagworms", and the article I carelessly linked seemed to indicate that bagworms were not at all like what I had. Further investigation pointed to the Eastern tent caterpillar, which definitely builds the right kind of cocoonish structure, and attaches to trees in the peach/plum/cherry genus prunus (and my tree is a chokecherry), and at least according to whoever wrote the WP article, is often erroneously called a bagworm. However, it still seemed not quite right, because the ETC builds its tents in the crotches of trees, while mine were at the ends of the branches, and the ETC does its thing in early spring, which was rather a few months ago.
Further googling solved it: yet another unrelated caterpillar, the Fall webworm, which is often mistaken for an ETC, but has all the properties of the actual thing in my tree. Formerly in my tree. And that was probably an overreaction, since most of the sites claim that the Fall webworm is mostly harmless other than aesthetically. Ah well.
"When asked, I describe myself as a ten of all trades." --Gary Leitzell
Posted by blahedo at 10:24pm on 3 Aug 2007