Let's have a little closer look at those leaves. Catalpa leaves. Ah. These must be catalpa worms!
Though I couldn't remember having seen a catalpa sphinx caterpillar,** I had heard of catalpa "worms" in plague proportions. Wow. Coolio! They were eating the everlovin' crap out of a small row of catalpa trees deep down Dean's Fork.
**I now know to qualify such statements as "Though I'd never seen a..." because chances are I have seen it, looked it up, maybe even blogged about it in my 2,009 posts to date. I just don't remember having seen this or that.
It was hard to see their true colors against the light, as they were all on the undersides of the leaves.
So I turned a low-hanging leaf over and wow! I could tell they were sphinx caterpillars by the prong on the tail. It makes a convincing false head, looking more headlike to me than the actual head, which is to the right. This might make a bird grab for the tail, which would certainly be less lethal than having a hard beak nip your head capsule.
The catalpa sphinx, Ceratomia catalpae, is the only common sphinx that's gregarious though the middle instars, according to David Wagner's Caterpillars of Eastern North America. Caterpillars come in two or three generations through much of its range, with mature caterpillars from late June to November.
Sorry--this is a zoomed up phone photo, best I could do. You should be able to make out two caterpillars, a healthy one on the left and a small black one on the right, dead center. It's covered with white parasitic wasp cocoons. I saw several like this. Nature strikes a balance. Or tries. I'm afraid this is it for the catalpa this summer, as it's too late for it to replace those leaves. It's having its own Early Autumn. (Know that standard? I love it so).