Hook Worm Hook Worms are part of phylum Nematoda and are any of a type of small parasite nematodes that have a hooked mouthpart that attaches to the intestine wall of the host. These worms have a pseudocoelom body cavity that lacks the muscles of coelomate animals that force food down the digestive tract, and thus depend on internal/external pressures and body movement to move food through their digestive tracts.