You found some CADDISFLY LARVAE!
Learn more about Caddisfly Larvae
This deep look video from PBS shows how a caddisfly larva makes its protective case.
Just like a caterpillar becomes a butterfly, the caddisfly larva will go through metamorphosis to become a caddisfly! Here is a video of a caddisfly emerging after its pupa stage.
Make Your Own Caddisfly Larva
You can make your own Caddisfly Larva using a printable template and a toilet paper roll. The printed Caddisfly Larvae can slip into the decorated toilet paper roll that acts as its case!