I found this opened gall with a gall fly larva inside, already in its pupal case. I think I may have scared off a squirrel who was after it. I am not sure if the larva is dead or alive.

The Goldenrod gall fly lays its eggs in Canada goldenrod (mostly), which eventually causes the large stem growths (balls) to be formed. Familiar to all I am sure. This is what lives inside them, and eventually turns into the fly, and the process starts again.

Please see here for the gall and the adult fly: http://www.pbase.com/laroseforest/image/131743789