Lots of insects make their living at least part of the time by skeletonizing leaves-that is,eating the choice lower epidermis and mesophyll layer of tissue but leaving the tougher leave veins. Today at Clinton Lake I noticed of skeletonized oak leaves. And it didn't take long to find the culprits hard at work.
These are very young saw fly larvae, probably scarlet oak sawfly larvae. I was thinking that these were real young but it looks like the mature sawfly is pretty small. Here's a link: http://na.fs.fed.us/spfo/pubs/pest_al/sawfly/sawfly.htm