caseworm vs larva

caseworm and larva both are nouns.

Word	Noun	Adjective	Verb	Adverb
caseworm	Yes	No	No	No
larva	Yes	No	No	No

As nouns, larva is a hypernym of caseworm; that is, larva is a word with a broader meaning than caseworm:

caseworm: insect larva that constructs a protective case around its body
larva: the immature free-living form of most invertebrates and amphibians and fish which at hatching from the egg is fundamentally unlike its parent and must metamorphose

caseworm (noun)	larva (noun)
insect larva that constructs a protective case around its body	the immature free-living form of most invertebrates and amphibians and fish which at hatching from the egg is fundamentally unlike its parent and must metamorphose