"the class was wriggling like a bucket full of catawba worms."
catawba worms
GNU Free Documentation Licensecatawba worms - Credit: geomerchant.net

Catawba worms are caterpillars used as fishing bait in the Southern states of America, especially for catching bream. The head is bitten off and the body skinned inside out, then attached to the fishing rod. These worms can be frozen and preserved for months.