I'd like to see a better picture of whatever it is under the leaf, if possible.

Anyway, there are lots of caterpillars that are perfectly happy to feed on geranium leaves. Perhaps if you go out hunting in the evening (with a flashlight), you'll find the culprits.

I'm sorry about that pic, I thought it was closer. I tried to get a closeup but then couldn't find the pic on my camera. These cameras are great, when you actually know how to work them.

I keep forgetting to check after dark. The leaf in the photo with all the doo doo on it is now half-eaten!

I'll try for a new pic again today.

I found it! The thing looked exactly like a twig. It caught my eye because it was dangling. It must have silk, like a spider. It's history, in the japanese beetle jar.