These are webs, the whitish structures in forks of trees and shrubs that house large numbers of crawly things. Some people call them web worms, tent worms, tent caterpillars or something like "yucky caterpillars."
There are different species, most the larval stage of moths. Some of these worms develop into large and beautiful moths. Most, though, become small drab brown moths. The worms are basically harmless except for eating leaves on trees. Rarely do they eat foliage to the extent the tree dies.
But most people find the webs and the worms themselves bothersome and unsightly.
You can do something about them. You can gather up a bunch of the worms and go catch some bream. You should feel better in doing it. No, you won't reduce the numbers of the worms or the webs, but you'll have a route to some enjoyable fishing and some nice food on the dinner table.
Start off this project by getting a small container. A plastic jar with a lid you can poke small holes in works well. Even a discarded drink container, 12-ounce or half-liter or 20-ounce size, is usable. Pick up a stick to assist in opening up the web.
Go to gathering worms. You may have an available youngster who can help make a game of it. Gather a bunch of the worms, and if several webs are nearby, this will be easy. Pick two or three green leaves, drop into the container then get ready for fishing.
You will want small hooks for your rod or pole and line. Open the container, shake out a worm and hook it. Toss it into the water. Just imagine if you are a bream and a wiggly green and black worm comes close instead of a dull red worm.
Experienced bream fishermen sometimes chum the area they want to worm for bream. They'll toss a few worms into the water then follow with the same on a hook.
When your web worms have produced a nice string of bluegill, red-ears or green sunfish for you, then you've got some good eating coming up to finish off this do-it-yourself project. And the bait didn't cost you anything.