It took me two days to figure it out. I zoomed it in with camera and binoculars and could not tell what it was. Sunshine finally gave it away. The white thing in the middle of picture way off in the distance. ( photo / image / picture from Donna S's Garden ) ( photo / image / picture from Donna S's Garden )
A plastic shopping bag that was blowing in the wind - Which got caught in the bush. Or that cow from Sesame Street TV show, the one which always wanted to jump over the moon - Yeah, this time it came crashing down, and so landed in that bush (after atmospheric reentry). Suddenly this turned from Sesame Street, into a bad Bruce Willis movie! http://www.youtube.com/watch?v=caRuhprYlOQ
The answer is bag worms, web worms or tent caterpillars It gets bigger every day. Glad it's not in my yard. ( photo / image / picture from Donna S's Garden )
As unsightly as they are they generally don't do enough damage to kill a tree. BUT if you get any on your plants spray with spinosad to control the nasty ugly things.
I always used rolled up newspaper and would light it with a match and burn them out. I had a small nest in a mulberry tree this spring and just clipped the limb off and burned it in the trash burner.
Break open the web, even if it isn't on your property they will get to you eventually. Then you can spray the caterpillars or let wasps feast on them for an organic treatment