Ephemeridae vs arthropod family

Ephemeridae and arthropod family both are nouns.

Word	Noun	Adjective	Verb	Adverb
Ephemeridae	Yes	No	No	No
arthropod family	Yes	No	No	No

As nouns, arthropod family is a hypernym of Ephemeridae; that is, arthropod family is a word with a broader meaning than Ephemeridae:

Ephemeridae (noun)	arthropod family (noun)
the family of mayflies (Ephemeridae)	any of the arthropods