dipterous insect vs order Diptera

dipterous insect and order Diptera both are nouns.

Word	Noun	Adjective	Verb	Adverb
dipterous insect	Yes	No	No	No
order Diptera	Yes	No	No	No

dipterous insect (noun)	order Diptera (noun)
insects having usually a single pair of functional wings (anterior pair) with the posterior pair reduced to small knobbed structures and mouth parts adapted for sucking or lapping or piercing	a large order of insects having a single pair of wings and sucking or piercing mouths; includes true flies and mosquitoes and gnats and crane flies