bloodworm vs polychaete worm

bloodworm and polychaete worm both are nouns.

Word	Noun	Adjective	Verb	Adverb
bloodworm	Yes	No	No	No
polychaete worm	Yes	No	No	No

As nouns, polychaete worm is a hypernym of bloodworm; that is, polychaete worm is a word with a broader meaning than bloodworm:

bloodworm: a segmented marine worm with bright red body; often used for bait
polychaete worm: chiefly marine annelids possessing both sexes and having paired appendages (parapodia) bearing bristles

Other hypernyms of bloodworm include polychaete, polychete, polychete worm.

bloodworm (noun)	polychaete worm (noun)
a segmented marine worm with bright red body; often used for bait	chiefly marine annelids possessing both sexes and having paired appendages (parapodia) bearing bristles