I don't know what kind of catepillars these are or if they turn into any type of pretty butterfly, but they can sure do damage to the trees. This is a neighbor's tree by the road. I noticed the webs while I was out walking. I had never looked quite as closely as I did at these, so I had never noticed that the catepillars seem to be eating the chlorophyll/green part of the leaves from the inside and leaving the membrane of the leaves intact. Not sure if you can tell what I'm talking about from the photo, but it is a bit amazing and creepy at the same time.