If a "Catawba" tree is what we call a "Caltalpa" tree, and I think it is, the worms get on the underside of the leaves, which they eat. Not all trees have them, but a lot do. They have black and yellow stripes against a white body. They are good fish bait. I have not used them for perch/bream, but they are good for catfish. If you worm them on a hook, they stay on real well. They can also be bagged up and frozen and used later.