member vs mouthpart

member and mouthpart both are nouns.

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

As nouns, mouthpart is a hyponym of member; that is, mouthpart is a word with a more specific, narrower meaning than member:

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

Other hyponyms of member include chelicera, fang, chela, claw, nipper, pincer, parapodium, fin, pleopod, swimmeret, limb, dactyl, digit.

member (noun)	mouthpart (noun)
an external body part that projects from the body	any part of the mouth of an insect or other arthropod especially one adapted to a specific way of feeding
the male sex organ
an organization that is a member of another organization (especially a state that belongs to a group of nations)
one of the persons who compose a social group (especially individuals who have joined and participate in a group organization)
anything that belongs to a set or class