mouthpart vs appendage

mouthpart and appendage both are nouns.

Word	Noun	Adjective	Verb	Adverb
mouthpart	Yes	No	No	No
appendage	Yes	No	No	No

As nouns, appendage is a hypernym of mouthpart; that is, appendage is a word with a broader meaning than mouthpart:

mouthpart: any part of the mouth of an insect or other arthropod especially one adapted to a specific way of feeding
appendage: an external body part that projects from the body

Other hypernyms of mouthpart include extremity, member.

mouthpart (noun)	appendage (noun)
any part of the mouth of an insect or other arthropod especially one adapted to a specific way of feeding	a part that is joined to something larger
	an external body part that projects from the body
	a natural prolongation or projection from a part of an organism either animal or plant