lepidopteran vs lepidopterous insect

lepidopteran and lepidopterous insect both are nouns.

Word	Noun	Adjective	Verb	Adverb
lepidopteran	Yes	No	No	No
lepidopterous insect	Yes	No	No	No

As nouns, lepidopteran and lepidopterous insect are synonyms defined as:

lepidopteran and lepidopterous insect: insect that in the adult state has four wings more or less covered with tiny scales

Other synonyms of lepidopteran include lepidopteron.

lepidopteran (noun)	lepidopterous insect (noun)
insect that in the adult state has four wings more or less covered with tiny scales	insect that in the adult state has four wings more or less covered with tiny scales