A small spider, if it were home, would probably pop out of there if the leaf were flexed.

Thank you Larry. I thought it might have been some kind of odd cocoon. Spiders are friends though, they get to stay.

You can see where I ripped the leaf poking around to see what it was, but I must have been more scary to the spider than to have peaked its curiosity.

Various caterpillars under the names leaf-roller, leaf-folder, and leaf-tier use webbing, but it deforms the leaf considerably. Certain spiders web and curl the leaf slightly, but they do not chew on it. With caterpillars, there is usually black specks of dried frass on nearby leaves.