mayfly vs ephemeropteran

mayfly and ephemeropteran both are nouns.

Word	Noun	Adjective	Verb	Adverb
mayfly	Yes	No	No	No
ephemeropteran	Yes	No	No	No

As nouns, ephemeropteran is a hypernym of mayfly; that is, ephemeropteran is a word with a broader meaning than mayfly:

mayfly: slender insect with delicate membranous wings having an aquatic larval stage and terrestrial adult stage usually lasting less than two days
ephemeropteran: short-lived insect

Other hypernyms of mayfly include ephemerid.

mayfly (noun)	ephemeropteran (noun)
slender insect with delicate membranous wings having an aquatic larval stage and terrestrial adult stage usually lasting less than two days	short-lived insect