order Ephemeroptera vs Ephemerida

order Ephemeroptera and Ephemerida both are nouns.

Word	Noun	Adjective	Verb	Adverb
order Ephemeroptera	Yes	No	No	No
Ephemerida	Yes	No	No	No

As nouns, order Ephemeroptera and Ephemerida are synonyms defined as:

order Ephemeroptera and Ephemerida: the order of mayflies or shadflies (Ephemeroptera, Ephemerida)

Other synonyms of order Ephemeroptera include Ephemeroptera, order Ephemerida.

order Ephemeroptera (noun)	Ephemerida (noun)
the order of mayflies or shadflies (Ephemeroptera, Ephemerida)	the order of mayflies or shadflies (Ephemeroptera, Ephemerida)