monarch butterfly vs milkweed butterfly

monarch butterfly and milkweed butterfly both are nouns.

Word	Noun	Adjective	Verb	Adverb
monarch butterfly	Yes	No	No	No
milkweed butterfly	Yes	No	No	No

As nouns, monarch butterfly and milkweed butterfly are synonyms defined as:

monarch butterfly and milkweed butterfly: large migratory American butterfly having deep orange wings with black and white markings; the larvae feed on milkweed

Other synonyms of monarch butterfly include Danaus plexippus, monarch.

monarch butterfly (noun)	milkweed butterfly (noun)
large migratory American butterfly having deep orange wings with black and white markings; the larvae feed on milkweed	large migratory American butterfly having deep orange wings with black and white markings; the larvae feed on milkweed